Check out a batch of high-res images from The Collector's museum from the Guardians of the Galaxy movie as well as a Blu-Ray featurette with Benicio del Toro below.
Among some of the Easter Eggs includes Cosmo, who in the Abnett and Lanning 2008 Guardians of the Galaxy comic was the head security officer at Knowhere as well as a telekinetic/psychic canine.
We also see the mighty god-like cosmic beings, the Celestials (Knowhere is actually a severed Celestial head).
A Chitauri (the aliens featured in The Avengers movie).
Some people think the creature in the red jump-suit may be Beta Ray Bill. Update: James Gunn said it's not Beta Ray Bill.
A Dark Elf (from Thor 2).
The Slither creatures from James Gunn's film.
Adam Warlock's Cocoon, and then there is Howard The Duck.
Who knows? Maybe the guys with the goggles are even the MCU version of The Watchers.