A assume you will be using the two left spaces (the blue) as menues and the main part for the content?

If so I would look at (in a design way) how those structures are going to react when they are made bigger by the contents they hold. I'm sure with tables or CSS you could make it look nice, but on every site I do I always get that bit wrong and find menues being placed where they shouldnt be, and find them stretching and losing all thier shape and style.

As you mentioned you will be changing the black background. The only thing I can think of is to keep it to a solid colour, or make the pattern very very small so it doesnt distract from the main part of the site. If it was my site the background would have a pattern smaller in size than "mesh/fishnet" border you have on the elements, something not to disimilar to the tiny pattern used here at SM froum for the background - also makes it very light to download, just a timy repeating gif.