>>1133
saving mspaint art as jpeg also wastes space, but that's not what you asked.

what determines whether a gif thumbnails properly or not is whether the frame is the same size as the image dimensions.
if you have a 450x350 gif and every frame is a full 450x350, it will thumbnail perfectly. the thing about gifs though, is you can also reduce file size by cropping frames to only be large enough to contain whatever pixels are changed from the previous frame. Frames that aren't the same size get fucked up by the scaler. I'm not entirely sure what it does to them yet, though.

Attached gif should break.

>>1140
Ok, so frames which aren't the same size will be scaled to fit within the dimenions of the thumbnail, based on the size of the original frame plus the offset from top left. For this particular one, there are frames which are smaller than the size of this thumbnail; these are rendered blank because they can't be scaled up.

Here's one that will render properly.

Actually, that doesn't answer your question either. I just used it as an excuse to figure out how exactly the software is broken.