I think this was touched on before, but I wanted to add to it.

The Endor AT-AT. The set piece that was used was obviously too small and posed in a weird position. I suggest replacing it with a digital matte, properly proportioned and lit, etc. Also, after Vader tells the AT-AT Commander to continue his search, the AT-AT is not heard or seen doing that. If the AT-AT could be shown walking away in the background with proper effects, that would be sweet. Also, after this scene, the AT-AT just disappears. Where did it go? Wouldn't it have come to the battle? I guess it was destroyed or knocked out of commission when the shield generator went up.

Just some thoughts.