Lofting your bed is amazing. Or, if you cant do that, get some expander thingies (bed bath and beyond has them) that raise the bed about 10 inches. You can fit a shit ton more stuff under there believe me.
Also christmas lights, lots of posters esp half ***** women.
If you plan on smoking non-tobacco cigarettes, invest in a SPOOF, a couple/few fans, lots of dryer sheets, febreze, and something to stuff under your door. if u really wanna be hardcore about it, get some duct tape and seal ur door up (all the edges). also burning lots of candles right up next to your door helps a lot.
and if you have room, buy some nice chillin chairs for your room. I had no room for them, but some nights we would have ~20ish people in our dorm, so places to sit are pretty sweet.