Here's some tips:
The label before the { } brackets will tell you which part of the layout you're editing. The text between the brackets is what's changing.
So the following code:
.primary {
background-color:#000000
}
This code is saying that to change the primary part of the layout, which are the navigation bar and sidebar colors. You're changing the background color of those two parts of the website.
I put this up to let people know which part does what. Needs improvement, but it's somewhat helpful hopefully:
http://wolfplaygame.com/forums.php?f=29&t=49737
The easiest way I've found to making palettes is to have an idea in mind. Most of my palettes are themes of nature, so it's easy to imagine what colors you would need for these particular themes. Fire conjures images of burning red and smoldering gray. Oceans are blue, and have sand in them, so this palette is blue and sand-colored.
To add a background picture, you can insert this attribute into any label:
background-image: url('LINK');
Spring Month: 3 
Night 
Flood Moon: 
