Hmmm... I'm really interested in this now... I took a crack at making that painting look as much like the screenshot as possible, with minimal effort. He's the result:

What I did is first off I resized the thing to the resolution of the game. Then I lowered the brightness and upped the contrast. Then with the "Replace Colour" tool in Adobe Photoshop, I replaced the yellows with an orangish colour, to resemble the screenshot more. Then I finally brought it down to 256.
Obviously there's still a lot of the grainyness, but it looks rather close to the actual background. I'm guessing the artists working on these background probably did somehting like I did above, then went in a touched up all the grainyness by hand (Err, mouse).
My major gripe was the amount of JPG artifacting on that original painting, haha. You can really see it now that the picture has been blown up.

What I did is first off I resized the thing to the resolution of the game. Then I lowered the brightness and upped the contrast. Then with the "Replace Colour" tool in Adobe Photoshop, I replaced the yellows with an orangish colour, to resemble the screenshot more. Then I finally brought it down to 256.
Obviously there's still a lot of the grainyness, but it looks rather close to the actual background. I'm guessing the artists working on these background probably did somehting like I did above, then went in a touched up all the grainyness by hand (Err, mouse).
My major gripe was the amount of JPG artifacting on that original painting, haha. You can really see it now that the picture has been blown up.