This is half of an image which combines with Rebekah Isaccs’ cover to create a panorama. See the interview and images at io9

Dark Horse requested that I use a more comic bookish look for these Spike covers, to create a better visual separation between my variants and the main cover art. I essentially used my sequential style, but I drew/colored it all in Photoshop rather than Illustrator, which had been my typical means of drawing sequential art. After finishing this cover, I realized I had gone a little too thick on some of the line art...so subsequent covers, for this series, will be on a line-weight diet.

By request, I'm adding the original line art, click through to see it...