If you are interested in fantasy/erotica art at all, if you haven't heard of Boris Vallejo...you should. His work, and that of his wife, Julie Bell, is some of the most beautiful of the genre. His paintings have been on the covers of dozens of science-fiction books and he also has his own line of calendars, which is how I first discovered his work.
Vallejo's preferred medium is oil paint on board, and he does his rough drafts in either ink or pencil sketches. He has been known to work together with his wife Julie on several paintings, as they have a very similar artistic style and work well together.
If you have ever played Dungeons and Dragons, you have no doubt ran across some of Vallejo's art.
You can find out more about Boris Vallejo by visiting the following websites, or picking up one of the many books of paintings by him & his wife at any fine book store near you.