Come to think of it, I did the same thing: I drilled some nice 3/8″ holes in the wall to hang my plasma. I also tore out some plants and put in some new ones.
I know for sure I will have to patch the holes in the wall when I leave, but – I would really feel it is in my best interest to fix up a place I am selling! I put a lot of work into the house I sold.
Renting is really not that different from buying, just a bit more liquid. You have an incentive to not do value-added improvements, but then again, maybe that is a good thing, because most improvements lose money anyway!