need hints on how to animate - not that I really want the cars to move, and not that moving cars on roads are invariably realistic, but its always amusing to increase pollution
Also, to animate, I recommend Macromedia Flash. MX should be pretty damn cheap on ebay these days, and it'll do what you want it to unless you have an intel mac.
Flash is good if you're making an animation frame by frame.
With IR you can create all the layers in Photoshop, export it, and your gif is practically done. I've never had a problem with filesize... Colour palettes and dither are your friends.