While your typical dungeon owner can't run out to Ikea and pick up a bunch of wall coverings and knick knacks, along with meatballs, to decorate the dungeon, there are still walls to cover, shelves to fill and tables to adorn. Don't let an opportunity go to waste; you might as well sprinkle some traps in there, like this one:
Self Portrait (CR 10)
A portrait is on the wall. The features of the face are fuzzy and indistinct.
Type: mechanical; Perception DC 34; Disable Device 34
Trigger Visual; Reset None
The viewer sees the portrait changing into his own likeness, then he is imprisoned as the spell. Once imprisoned, the portrait becomes a portrait of the character. Imprisonment (DC 23 Will Save or become imprisoned in the portrait as per the spell)
Of course, you shouldn't put just one portrait in the room, and you should give the characters a reason for looking at the portraits. Perhaps they have been told that one of the portraits contains a phrase they need to activate an artifact. Maybe one of them has a clue to finding hidden treasure. If you build this up, when the portrait begins to change, they may even think they have stumbled onto the correct painting to help them, even though you'll know they haven't.
As a bonus, if they can't break the spell right away, it would be pretty cool to have a portrait of your character, wouldn't it?