Here are some of the suggestions I have transferred from the ESB:R thread, and some new ones as well:
-Grey TIE fighters (similar to ANH)
-Reduce blue on Executor during reveal scene (such as in example http://img380.imageshack.us/img380/9471/executorcolourdifferencmu1.jpg)
-New shots of Falcon and TIEs in the asteroids (similar to shots of Falcon and TIEs in ANH:R)
-New asteroids???
-Fix asteroid collisions/explosions in space (they collide, but shouldn't explode unless hit by a laser or there is some sort of hot gas inside them)
-Fix explosions on asteroids on shot where Star Destroyer blasts them with its lasers
-Shots of Luke's X-wing entering and exiting hyperspace (now that we've never seen before at all)
-Adding some of those hot-air balloon thingys and tibanna gas refineries to the initial far-away reveal of Cloud City with approaching Falcon
-Adding ship traffic (other than Millenium Falcon & Cloud Cars) to Cloud City
-Adding the missing Mon-Calamari class cruisers to the end scene (all I can see there are the bulky rebel transports, the medical frigate and some starfighters)
-Adding A-Wings, B-Wings and other small rebel ships to the end scene
-Adding more starfighters to the end scene
-New shot of Millenium Falcon approaching landing pad from behind? (possibly to replace the CGI shots where the Falcon looks sorta 'flat')
-Improvising the sunrise-from-space effects when you see the Falcon leaving Bespin being chased by TIEs
-Tauntauns running faster (possibly to reduce the stop-motion effect)