Putting together a gallery wall

After 3 months of staring at this blank wall and the pile of frames and pictures on the floor nearby, I put the little one to bed early and got my gallery on.  Actually, the fact that Brian had finished painting was part of the deal, we had some stuff on the walls, then he took it down to patch them all up (they were in pretty random spots for the size art we bring to the place) and give it a fresh coat of paint because this was the only room in the house that was not "freshly painted" when we moved in.  Freshly painted gets quotes - that's another story.  There is painted trim throughout the house, except in this room.  The estate had all the walls painted, but not the trim, and the trim is pretty rough looking.  We'll get working on that one of theses days.  Gotta decided where to start and what colors to use.  Don't want to paint anything that's getting dramatically changed sooner than later...

Back to my gallery wall.

Before, big empty wall above the desk.

Layout testing on the floor, quick paper cutout to model the light.

It's up!  I've missed having my clock on the wall.

Figuring out the mantle next door, progress.

The whole corner is looking better, still has a ways to go.

I have ideas about that weird TV hole on the left side of this picture.  I want to get a giant, light colored canvas print (DIY art?) to put over that opening.  I want to do some work to lighten up the feel with all that dark wood, without touching the dark wood.  I think it's darker in these pictures since I was doing this work (and photos) late at night, the wood feels a little brighter than this in real life.
We stuck with white paint for these upper walls because of the dark wood.  We want to keep it light with all the dark wood and few windows.  This room is "done" for now.  We've updated the light fixtures, changed out the door knobs, added the carpet, hung some pictures...  Feeling pretty good about this one.
I considered putting pictures on walls in several other rooms, but found that to be very challenging due to really hard plaster.  Any suggestions??  That plaster is hard stuff - I bent a nail trying to get a picture hung in Noah's room...