Don't know of anything that allows you to add things like secret doors, but the author of the Positioner also has a furnishings mod that's intended to be a companion to it.
He also has a renamer mod that allows you to rename items which is cool for identifying the trophies in your display cases (Ulfric's Sword, Morokai's Dagger, etc). I use it with a separate mod that causes dragons, giants and trolls to drop skulls to rename the dragon skulls after the named dragon who dropped them. Mounted over the front door of my Lakeview Manor is "Mirmulnir's Skull" ... the skull of the first dragon my character killed.