Your surround speakers are not in an great place from the looks of it. It might sound better to get some bookshelf speakers and mount them high. It's not a big deal though since the surround channels don't usually do a whole lot.
I'll agree (sort of) then disagree (sort of) with shady. Those really aren't surround channels with the way they're set up, they're rear surround channels. If you're receiver has the option for rear surround that would be better. Also, ideally, you want them parallel with the front L/R so they form a rectangle. Looks like that would be an issue placement wise, but I think you may be able to do a little better.
The towers aren't a bad choice because it puts the drivers closer to ear level, which is good. I'll also say that it really depends on what content you're playing that determines how much is coming through the surround channels. If you're watching TV or something like that, then you probably won't hear a ton of content coming through those channels, but if you're watching blu-rays (especially movies like Avatar, Transformers, etc) you'll hear a TON of content coming through the surround channels.