IGN has a description of the footage shown at the panel:
"And what producer Kevin Feige, director James Gunn, and the cast did have to show the crowd was pretty great. Chris Pratt's Star-Lord is not earthbound when we first see him in this sizzle reel, even though he is very clearly of Earth. He has an iPod, listens to "Hooked on a Feeling" (which becomes the main music of the piece eventually), and can give the finger with the best of them. He gets caught stealing some kind of alien orb and is arrested by Djimon Hounsou's Korath (revealed as a member of the cast just tonight).
Thrown in an intergalactic booking station, Star-Lord winds up alongside the other criminals who will become the Guardians of the Galaxy: Zoe Saldana's very green Gamora, Dave Bautista's green with some reddish highlights Drax, the tree-man Groot, and the little spitfire Rocket Raccoon. The five of them wind up in a Usual Suspects kind of police line-up shot, which is the great moment that the reel crescendos with, but we also get to see the group in action, including the CGI Groot and Rocket. They look perfect, although we still haven't heard their voices and don't know who will play them.
The practical make-up on Gamora and Drax also nails the look of the comics, and we even got a glimpse of Star-Lord in his famed helmet at one point. And the tone of the whole thing is unique -- funny, strange, and kind of out there. Very James Gunn! Marvel is definitely pushing in a new direction with this one."