I've built a couple.
I got your basic cut to size quick change frame off eBay. I'm don't recall who the seller was, but he was a retired military sniper that happened to live within an hour from me.
Then I built out the frames with 1/2" MDF 1" wide that I turned on it's side (for 1" space away from the wall", and simply longer mounting screws going through the frame, through the MDF, and into the drywall.
For backlight, I tried cold cathodes from a computer store. I thought it would work, but they were not diffused well enough and left hot (Bright) spots. I upgraded to a pair of thin 24" flourescent tubes top and bottom which was better, but really expensive.
It's been suggested to me to try rope light next time. I think a good LED rope light would rock if I don't need a large (And ugly) power transformer hanging on the wall.
Sorry I don't have photos of all of this...I've moved recently and the frames and everything are all packed up.