The incomparable Mr. Michael Whelan. I have to admit, I was expecting him to knock himself out for this and "Wow!" was all I could say.
Wesley Allsbrook's amazing line drawings. We at Tor are huge Wesley fans. Go check out her comics, The Leviathan and Montmartre à trois.
And Francis Vallejo. I only have a few more weeks to say this so I will say it again: Holy Cow, I can't believe this kid is still in school. Francis is destined to be an illustration superstar.