1) red and gold curtains, comforter. Maybe specifically Hogwarts/Gryffendor pillow cases, if they're available.
2) The three or so different Gryf tapestries and wall-hangings.
3) If I can afford it, the replica of Gryffendor's Sword. That may have to wait a while, it's like $170. On the other paw, since Wizards of the Coast isn't making any new D&D books, I've got more cash than usual :) This is a luxury item, though.
4) Maybe a coat rack with a class robe and the red/gold scarf.
5) It would be neat if I could get a blank megaphone and have one of my artsy friends paint the Gryff lion on it, or find some school that has orange and gold for its colors and get a set of their pompoms.
What else would really set off the theme?