Yeah, I'm not sold on that concept art either. Rocket Raccoon will be hard to do convincingly and not seem cartoony.
Speaking for myself, I'd rather see Bug, in the movie as I was a huge fan of the old Micronauts comic. In fact, Marvel-- Do a Micronauts movie insteasd! Of course, they couldn't use the name "Micronauts", which takes away name recognition the movie may or may not have with Joe Blow movie-goer, but it could still make an awesome movie.