Hey pete,
You want to mount rear speakers so the tweeter is at or slightly above ear level when seated, same as your mains. Since your seating is against the wall, the surrounds almost have to face each other, more or less. Its not the preferred method, but sometimes it's the only option. If the wire running down the wall is not something you can live with, there are options.
1: Get some flat plastic wire (raceway) tracks to run down the wall. You should be able to find it at a home improvement store or office supply. The wire runs inside the track and the track can be painted same color as the wall. Not perfect, but less noticeable.
2: I believe electricians have handy tools for running wire in finished walls. I think its called a "flex bit". You can then pull wire and mount a terminal for connections where you plan to place the speaker without tearing up your walls. A friend of mine had this done. I can't be too much more specific about it as I have not seen the process, but he said it was relatively simple. His brother in law was the electrician, so I can't attest to the cost either. Ask an electrician and see if that sounds right. In fact, it might be a wise choice to have a certified electrician do the work. I'd hate to see you drill through some existing wiring.
A pair of speaker brackets should solve your mounting issue. Take a look at something like this.
http://www.amazon.com/gp/aw/d/B000X9O8SI/ref=s9_top_hm_b1FUB_g23_i1
The mount you choose will depend on speaker size and whether or not the speaker has provisions for mounting.