It took me a minute to realize that the silhouette was taking a picture. Maybe put a little more detail on him, or don't make him so dark, because he kind of looks like a alien shaped hole. I really like it other than that.
Oh, i didn't understand why one of the aliens was WITH the astronauts saying hi to another alien...please make the other alien stand out more as taking a picture (perhaps with the spacemen being all goofy and the alien with them putting some rabbgit ears over a helemt or something- and you've got t-shirt gold, mister.
Had to read the above comments to understand what was going on!!!
It's really not obvious that the alien in the foreground is taking a picture...
Make that more obvious, and then (similar to comment above) - have the astronauts in a more comical photo pose.
Also, you could have some other aliens (making fun of the spacemen - rabbit eras etc), but in a special glow ink, so they can only be seen in certain lighting conditions...?
About my design