In my experience, whenever I move I have a difficult time hanging art and photos on the walls. I'm usually afraid I'll change my mind about what I want where and be stuck with off-center wall art or ugly holes. This results in numerous pieces leaning against the walls for the first few months until I finally take the plunge and nail 'em up.
One solution I've learned is to put up some shallow picture ledges. This way, there's no worry about switching up the art, and I even add small vases and other narrow decor items so that it can change with the seasons, with my mood, or when I've added a new piece of furniture. A long ledge above the couch is a personal favorite of mine, since it typically stays put. If you're as noncommittal with art as me, do you have any tricks?