I always cringe when I see indoor Access Points installed vertically on walls. Yes, I know this is supported on some models, but I always try to mount them horizontally. Sometimes the ceiling is too high or consists of a material like metal or cement that you can't install the AP to and you have to mount the AP on the wall. Here's a wall mount kit from Ventev that I have been using to install APs on a wall.
The holes on the AP mounting bracket for the new indoor CW916X APs and traditional Cisco APs doesn't line up with the holes on the wall mount kit, so I had to drill a couple of holes in the AP bracket to get it connected correctly. Easily done.
The wall mount kit can mount directly to a wall or to an outlet box already installed in a wall.
This model has a cover that flips up so you can access the inside of the kit to mount it to the wall.
I only use this kit on wood or sheet rock walls. You should not mount this on a metal wall as too much of the wireless signal will likely be reflected back quickly to the AP.
The installed kit and AP look very professional in my opinion.