Speakers placement suggestions

One of my customer want to renovate his TV room. He want to install a home theater speaker System.

I already installed ceilling speaker in the kitchen, dinning room and the living room. He want in ceilling speaker in that room too. Look for the green circle near the foyer.

My question about rear surround speakers placement:

The room is about 10 by 18. On the room drowing, speakers are in light blue. Should I install on the wall speakers and at what height? Or in ceilling rear surround speakers?

My question about center speakers placement:

We will install an 40" LCD TV over the fireplace. At first i was planning to install the center speaker just over the fireplace, under the LCD. But my client want an LCD wall mount that can pan, tilt, swivel and have some Height adjustment. He want to be able to lower the LCD Panel when not using the fireplace to have a more natural Height.

I don't know if there are wall mount system that can do this? And if yes, when he will lower the panel, the front speaker will get behind the screen. I think that the speaker should be install with the LCD on the wall mount so that both the LCD and the center speaker move the same way.

Any products idea?