Did this composite test of Spike as the potential Twilight - it's a very good match - take a look, see what you think. Not that I particularly believe that Spike will be Twilight, but he sure matches up with the preview artwork.
Hope you will take a look - it's a composite from "Sleeper" (alley scene) and the Original Preview image -
link for large original image at flickr: http://www.flickr.com/photos/nmcil/4235930724/sizes/o/
click on image for larger view -