While looking around, I came across Tor-Forge’s Fall 2010 Catalog (PDF). On page 47, what I suspect to be a draft of the cover art for the re-release of the first Wild Cards is on display in black and white,. It depicts the doomed, heroic character of Jetboy, a hero at the center of the release of the Wild Cards virus.
At a guess—I’ll remark on Twitter if I get confirmation—I believe the painting is by Michael Komarck, who has provided art for the new Wild Cards trilogy.