When you were a kid, what posters and pictures adorned your room's walls -- TV/movie stars, singers/bands, athletes, Einstein, bio-hazard warning signs? Why were they worthy of display (and did your parents ever yell at you to take them down)?
Heh, my room is still covered in posters and I'm 22. Doctor Who on the wall, X-Men: First Class on the closet door, and my old Stargate: Universe 2011 calendar that I still can't bear to take down (it has a 2012 page, okay? It's still good!). Plus my roommate has a Lord of the Rings poster and a picture of a dragon I drew for her a while ago.
We are the very definition of mature adults, clearly. :D