Onwall/Inwall speakers
Check out the on-wall speakers from Paradigm and Axiom audio. They might be a good comprimise of esthetics and performance. RBH sound also makes some good on-wall and in-wall models.
Keep in mind that the surround speakers are located on the sides of the listening position, and not in the back. For these channels, many manufacturers offer a bipole or dipole type speaker that will mount flush to the wall and will perform much better than a direct radiating inwall speaker.
For LFE bellow 30 Hz, you should also consider a 10" or 12" sub if it passes the WAF.