Can I have an animated GIF with more than 256 colours per frame? I want to do an animated GIF but the limited colour pallet is making it look like rubbish.
Yes, you can, with certain limitations.
GIF supports per-frame (local) palettes and has "as-is" frame disposal method which allows combining of several frames.
These two features together allow GIF to have more than 256 colors at a time. The catch is you can only take advantage of this when not all pixels of the image change between frames.
So if you have something moving in front of a still background, you can have more than 256-color animation — the moving object will be limited to 256 colors, but the background could be composed of several frames with different palettes.
At least in theory you can stack gifs and make the extra colors transparent.
First you copy each frame so that you have 2 of each. Then select the area by color with the sensitivity low enough so that it selects half the picture. Then just errase everything inside the selection. Now invert the selection. Then go to the next frame. And errase everything again. Save the end result. raw-ani.gif Delete half the frames. Save with a new file name. ani1.gif Load the the previously saved version. Delete the other half of the frames. Save again. ani2.gif
Hack some html with absolute positioning and put ani2.gif on top of ani1.gif
Repeat the process to make 4 layers, 8, 16, what you want
You could also speed up the raw-ani.gif result and have what porneL described.