Light in my living room is dim, planning to get tiles on three walls. Would like to know what color scheme shall I choose?

I would do gray walls and just make sure it has the same undertone as the tile I often paint the ceiling the same as the walls if going with a light color or if a little darker for walls I cut wall color 50% for the ceiling. I have a gray and mostly white LR and I have walls a color called Vancouver Day from C2 I then add color for different times of the year with pillows and a few accessories The wall behind the sofas I just painted in a purple from one of the pieces of art and I love it.

This will help get some light into the middle of your space. http://www.westelm.com/m/products/overarching-floor-lamp-antique-bronze-w890/?pkey=cfloor-lamps You could also do end tables or a console behind the couch and place table lamps on either. It doesn't look like you have any seating near the edge of your space and your existing lighting seems to be positioned at the edges of the room. So I'm not sure if sconces would help much.

Let your wooden beam be as it is. put your Led lights in the other direction ( two on each side in one rectangle , so the total will be 16 units of say 10 watt each Led.), as to balance the horizontal and vertical shape. Don't put anything on the wooden beam to retain its the beauty.