Customization

I've been trying to customize my blog. For all of you who wonder where my gadgets and gizmos keep disappearing to, well, I accidentally saved without putting them back on. I'll get them back up when I get the background correctly fixed.

I'd like the blog to look colorful, but not overly artsy. After trying many backgrounds, some I like and some I hated, I have an idea of what I want but can't quite figure out how to do it.

I'd like to get something like this

or like this

centered and stretched across the screen. Anyone out there know how to do this?