Killroy, you could put up a piece of plywood over the drywall and create a whole wall surface to nail or screw to, and not need to worry about hitting studs. Now that would mean
you want a finish over the plywood but that could be anything from painted anaglypta wallpaper, to wood forms or even a couple of boxes of end of line wood floor, to tile, to brick,
to mdf wave wall, or anything else you can come up with.
One of the simpler detailing ideas I have thought about for my small feature wall is to simply cut some angled lines in a sheet of drywall, and paint it. You do have a lot of area behind
those hdtv sets, to screw to studs, to create a surface to screw to.
And if you shimmed the tv frame out from the wall, you can leave the bottom and top open for ventilation, while creating depth for the tv's electrical plug. You also need some plan
for being to remove the lightbox, for any tv maintenance.