Craig Mullins is considered by many THE master of digital painting. He was one of the pioneers on the field and his work is breathtaking, it is very realistic but also has a very painterly style. He has done concept art for big videogames, movies, card games, etc.
Some of the illustrations I like the most of him are the ones he did for the PC game Age of Empires 3 and its expansions, where he depicted very realistically the ancient civilizations such as the Mayans, Aztecs and the medieval Europe as well as Asian cultures.
He has a huge amount of work, you should definitely check out his website which actually, when it was updated and released, the server went down due to the huge amount of artists checking it out.