There are currently 2 NPC's you have have one is a failed dimension engineer and the other one a bartender, the bartender lines up drinks across his bar when you talk to him and drinking them gives you the standard 'drunk' effect, in the guld dimensions you can have NPC's that offer the guild weekly quests.
From doing great hunt RIFT achievements there are various models of bosses you can have in your dimension that are on statue's, but you can drag the statue's underground so the models just stand on whatever terain it is, unfortunately these have no interaction, but you can play about with them to make some cool looking scene's and also from defeating volan you can get a great big Helmet of Volan to shove in your dimension.
Training dummies in dimensions is something that has been mentioned a LOT on the forums, so It is extremley likely that we are going to see these in the upcoming months. I mean with this addition to RIFT literally the sky is the limit and I am really excited to see what will be added to them in the upcoming months!