Nice start here!
Haha, my dA account is here: http://dokijack.deviantart.com/ :)

To get a picture as your background, you go to "My Layout" under your settings. Go to the very bottom to the override helper. Click on the button that says "Page Background." Above that, there should be a text box and a "save" button. Paste the URL of the image you want as your background into that text box and hit "save." If you want the background to repeat, you click on the button that says "page background-repeat" then in the text box type in "repeat" then hit save again.

The content background colour is the one that sits behind all of your tables, but in front of your background. I thought it was annoying because it covered my background image, so what you do is in "My Layout," there are colour options off to the side. It should be the second one down. Instead of having a hex code in the box, replace is with an asterisk [*]. That should make it disappear.

There's a great override tutorial if you want to do more stuffs! http://www.sheezyart.com/view/129436/
Have fun!