+2  A: 

The white-on-dark look makes the content look boxed to me. Maybe you could use another color, but not have as much contrast between the two.

Honestly your users will probably care more about the quality of your service than the colors you choose as your background. If your service is compelling it won't matter unless the colors are garishly ugly.

As far as flow-layout, it's always a good idea to support higher resolutions, but only if it makes sense. By that I mean that some content (e.g. large amounts of text) have upper limits on line width which affect readability so your flow layout has to be smart -- it can't just be width=100% or some such shortcut.

Another thing I would keep in mind if you're creating a service to be used by all people is allow for SMALLER than 1024x768. By that I mean larger fonts crammed into that resolution. Some people can't see so well and the wider the demographic, the more flexible your layout should be.

My .02

micahtan
A: 

1) By having a white area surrounded by color, you are leading the users' eyes there, which helps them focus. Therefore it is OK.

2) With online stores, 2-3% of the audience means 2-3% more money. So make sure you investigate the user demographics in order to understand which screen resolutions they are using and try to accommodate them.

3) If going with a liquid layout, keep in mind that readable text is at maximum 100 characters long (some may argue that even that value is too big).

Flavius Stef
A: 

From a cognitive point of view, I'm not sure that your users will even notice the background. Although the high-contrast in the footer will work well.

From a usability point of view, what information did you get out of your initial user groups?

AdamC