Well I was doing this game for awhile and as I work alone I have to cut corners every now and then to save time. Also this game would have been dark in tones so the realistic style would be good. I used royalty free photographs, cutted them in photoshop, and did quick paintovers and I think I got pretty good results. It did take some time, but I'm sure it took less time then making them all by hand. Plus I suck at drawing so there you go
The background doesn't mesh as well as it should but this was just a WIP. Here's an example:

EDIT: Oh yeah, to answer the original question I just took photographs that suited. Cutted them with magnetic lasso, magic wand or quick selection. After that I resized and after that I painted over. Without the paintover they would've looked even more "resized" so that's a must. At some point you have to try the sprite to your BG and change hue and lighting values so that the sprite will fit in. So if you have a car photographed at sunset it will most likely not mesh as a car at daylight. So you have to tweak that by hand whatever is the situation.


EDIT: Oh yeah, to answer the original question I just took photographs that suited. Cutted them with magnetic lasso, magic wand or quick selection. After that I resized and after that I painted over. Without the paintover they would've looked even more "resized" so that's a must. At some point you have to try the sprite to your BG and change hue and lighting values so that the sprite will fit in. So if you have a car photographed at sunset it will most likely not mesh as a car at daylight. So you have to tweak that by hand whatever is the situation.