Jim,
Like Tony said above there is really no source for designing styles; however, you can learn some of the skills to create them by looking at various tutorials, I would reccomend these two:
http://robouk.mchost.com/
http://www.pixeljunction.com
Other than that I learned alot through looking at modified boards and deciding what I like, what I don't, etc.
You can contact me if you want any further help