I can create covers or maps for RPG books. My cover designs are similar to the look of the D&D 3/3.5 manuals in case that is a style you might be interested in having on your book. For an example of what I'm talking about, here's a link to my portfolio:
http://www.animagnum.com/?p=242
The above link goes to a 3D render, which is one approach I could take (e.g., make a model of the cover and then do orthographic renders for the front, back and spine of the book). I can also send you links to my map work in case anyone is interested.