Color Background
For just one color as your background, you can choose to use either words colors or hex color codes. That is, you can choose one of the following:
Image Background
Image backgrounds are easy to display, but the effect is completely up to the image. If an image is made for a tiled background, then it would look great, especially if you add in tables for your layout. If it's not made for tiling and you just threw something together, it might not turn out so well.
To display a tiled background, use the following code:
Combining Properties
I don't see much point in this but sometimes if your background image takes too long to load but you think that having a white background is too ugly, you can always add a color underneath your background image so that people will see some color while your image loads.