Been out of real practice for a LONG time but practiced most of my time in my hallway when I lived at home so I feel suited to answer.
Do you have space to the side? Regular ceiling height or more room? You could put cardboard against the walls to not smash them up too bad.
Dk your exact level but slackstuff works well indoors (any yoyostyle trick). Some suicides and integrals (if you have the height/width required). Bodycombos work (I learned between/over the leg bounces in my hallway). Multiple diabolos and string control tricks ofcourse. If you can do two diabolos ("relative beginner"?) then there are quite a few tricks that can be done. Stopovers/infinite backwraps, vortex, slacks, suns, grinds you name it.