I don't (yet) have a complete (marketable) book manuscript yet, but I already know that Dominik Mayer would be on the short list of people I'd beg a publisher to hire for the cover. Hell, I'd write a book just based on some of his illustrations. The intensity and lushness of his images is evocative of gaming and film cinematography.
PS - When I first wrote this entry, I typed that Dominik is one of the people "I'd bed a publisher to hire for the cover." Still accurate.