My room is approx 17' wide by 20' long and will be used for both home theater and gathering/living room.

I plan on putting in a 56-65" DLP tv eventually against the wall that is 17' wide. It will be centered on that wall.

I would like to use sconces and I'm trying to determine where to put them. I know that I am going to put 2 or 3 along each side wall but I was wondering if I should also put a couple on the wall with the tv? Maybe a couple of feet out from the corner of the wall?

I wasn't sure if this would look okay or not. Please advise.

IMHO, too many of the same light fixtures in a general purpose gathering room won't look good. Mix it up with recessed lights, sconces, lamps, up lighting behind a plant, cabinet lighting, Add a cornice with up lighting etc, lighted art on the walls, an ambient light system behind your display.

In other words limit the sconces to one or two walls. I think unless you are going for a theater look I would only put them on one wall.