Nice to meet you, Reaxan.
Really good points, Keiko! I'm definitely with you on the fact that fancy tools don't mean fancy image. I personally think all you basically need is brushes, like with real painting. They can be any kind, depending on preference. MSPaint
I think the key to the style your after is correct tools. Basically the images aren't very complex in any way. With very few strokes you can make good looking image. At first it seems harder than it actually is, which hopefully is encouraging. Anyway, I just tried out the method I've always used when trying to mimic a style - painting over. Here it is step by step.First, naturally, observe the style. Find images of the game and perhaps save them on your harddrive. Look at them fullscreen with an image-viewing application. I actually have tens of screenshots on my HD of Monkey Island 1, 2 and 3, DOTT, Sam And Max and probably of some others as well. It's really educative.
Try to figure out how the images are made. For example the specific Sierra's style you're after probably is originally achieved by scanning oil-paintings and reducing the color amount to 256. Basically, if you want to work on the computer, just use similar kind of brushes. I think regular round, sharp and soft brushes will do the trick. However, if you'd like to add the grainy hue variation, you could use custom brushes in Painter or Photoshop, if you want. But that's not really essential, it merely makes the image a bit more full and alive.
Anyway, to start off the mimicing, get an image you like and open it in your favourite painting program. As we're merely trying to mimic the style, no trying to educate ourselves in composition or anything else, just take a portion of the image and paint over it, trying to copy it. I selected this image I found from Mobygames.com, I took it because there's the kind of an empty wall that will demonstrate the simpliness of the process well.
I'm going to focus on the wall on the left. Select the wall with a selection tool (make sure it has anti-aliased edges) and fill it with the shadow color. You can pick the color with an eye-dropper tool. The reason why you pick the shadow color is that, in my opinion it's good to work from dark shades to lighter ones gradually. Even better, from mid values (brightness) to extreme values. Kind of adding contrast all the time until you're satisfied with it. Also, as you get more comfortable with it, you'll notice that as a color gets lighter, the color subtly changes. When you work your way up gradually, you'll be able to change the color respectively. However, that's not important right now. It's just good to try and learn the easiest techniques from the beginning.
After you've got the base color down, you can block in the main colors. Basically first the one for the lit area and then a dark one to make the upper part of the shadow a bit darker. The latter one might seem unreasoned and confusing at this point, but it's just something light does. You can leave it out, don't be put off by it. As for the color-picking, often it is recommended to pick the colors by yourself from your painting program's palette (because when you work on an image from the top of your head, you won't have direct reference), but I know from my own experience that finding the right colors in the beginning is VERY challenging. That's why you can take a shortcut and use the eye-dropper tool to pick the color and see where the color is found in the palette and try to see a relation between the colors in shadow, and the ones in light.
As for the actual drawing part, try to find a brush that lets you get off as easily as possible, still getting the desired effect. For the border of the shadow and the lit part, you want a smooth edge. It would take lots of blending if you were to use a sharp-edged brush, but you won't have to deal with that because you'll be using a soft brush. You will optimally only need one stroke for the edge. Then just fill the rest of the lit area. Also, for the dark shade in the shadow, you would just use a bigger brush and a single stroke. It's easy to get too complicated with this.
Next, we'll add the subtle lighter part of the lit area. This is because the closer the surface is to the light, the brighter it is. In this image, in my opinion, the way the light goes is not quite natural (not that I knew that well anyway) but it looks really good so it doesn't matter. You can either use once again the eye-dropper for the color (you have the same wall on the right which you can use for color-picking) and see how the Sierra's artist chose it according to original bright blue color. Or, you can just pick the blue color and make it a bit lighter with the palette options in your painting program. In Photoshop, you just double-click the foreground color that shows on the toolbar and the palette window pops up.
In the next image, there's an example of how you could move the brush around to minimize the amount of strokes. I tried to demonstrate it with the red lines. The topmost line is with the light blue, and the bottom one is using the
original blue color to cover any misstrokes. This way you don't have to be perfect first, you can just 'erase' the excessive color with the original one. If you're wondering, less strokes doesn't really mean a better result, but it
means faster workflow, which is always good for images that have lots of detail.
Next, I added the reflection-kind bright blue edge. I just removed the selection that was earlier keeping me from accidentally painting on the background. Then I picked the bright blue color and used the generic line tool
to make the lines. Simple and very accurate.
I also added the ceiling there. I just picked the dark shadow color and painted the ceiling with it. Well, actually I used the path tools to get as smooth edge as possible, but at this point, you can equally well use a sharp-edged brush for
Now, we're going to work on the detail a bit - the light. Here you get to see in action what I meant by the gradual coloring. This is due to the lens effect (I think) that you seen in pictures. The center of the highlight is white, and near the edges of the highlight you see the actual color of the light, a bit exaggeratedly. You will start with coloring the actual color of the light with bright blue (see the actual colors I used in the boxes on the image). Just block in the hape of the light. Next with a bit brighter color (it's actually also a bit more cyan - details, details), paint on the shape of the light, but so that the very edges are of the previous color. See the middle of the image for this phase. Finally, you'll add the white, or nearly white, center for the light.
You'll see that in the end, the middle phase doesn't change much. However, with gradients of larger size, the effect is very noticeable. It takes time, however, to learn what kind of colors you should use for the gradations. I'm still trying to learn. Color theory is your friend on this one. As well as photo reference.
And here it is on its rightful place. I also added the edge that is between the wall and the ceiling. Again, I used the line tool but this time it was two pixels wide. I also used a Photoshop trick on coloring the red and the blue parts. This is something that is irrelevant at this point, but I drew the line on a separate layer and used the 'lock pixels' feature. It locks the pixels' transparency so that you can color it any way you want - you won't be able to cross the edges of the shape (line). But that's just something I've learned to use to speed up the process. You can use a regular small brush to paint with the red color manually on the line.
Here are the rest of the images I have. It so happened that when I was finished with my post, the board said my post was too long and that I should go back and edit it. When I hit the back button and refresh, this is the last version I get. Luckily, I saved this version on the notepad (screwed up the formatting, by the way). So, instead of typing the rest, I'll just post the images and edit later to add the comments. I hope this is of some use as it is right now. Good luck!