Basically, Oddmuse is a web site like any other – all general techniques for creating style sheets for web sites apply. You will probably need to learn at least the basics of writing Cascading Style Sheets. On this page are listed some resources that might ease the task:
It’s also a good idea to just look at the styles available on this site and see how they are made.
You will probably need some graphics to spice up your design. Here are some resources you might find handy: