Hello cavingman. Nice room.
Ok, first of all, I am the farthest thing from a CI you can imagine. Take with salt.
The layout is everything. Yeah, you know that already. So... I would finalize your seating postion before continuing. In a closed rectangular room, 38% distance from the front or back wall is recommended. Since this is not totally symmetrical, it may or may not be less accurate, but Id imagine its still a good number to try out. Or what I really mean to say is that I wouldn't
aim for 50% distance. Now, this is the audio-first point of view.
Video first, you can go by desired viewing angle. Have you seen the calculator I've linked countless times here? Now, it is a reference, but personal preference is everything.
http://myhometheater.homestead.com/viewingdistancecalculator.html
One of our local CI experts here has stated that he often just has the wire sticking out of the walls. He says it common. I suppose this "ugliness" might be easier to remove than an actual plate, if you ever changed the setup.
Regarding speaker placements, try to get both equal distances and equal angles. So, the colummn I suppose looks better from what I can tell, but I have no advice for you on running the wire.
You should also realize that the right surround, or in fact just the right of the soundstage, might sound stronger or heavier. Because of the reflections from the closer wall may reinforce volume. Treatments can ameliorate that for sure. I know firsthand.
For the surrounds, typically 90 to 110 degrees is recommended. Some really believe in 90, especially if you are going to run rear speakers as well. Good luck.
