I have dedicated a section on weedhopper.org for free, full-size Droid wallpapers. The perma-link is here: http://www.weedhopper.org/droid/
Currently, the page/site isn't very mobile-friendly, and the droid wallpaper page is pretty much cut off from the rest of the site for the time being (have not added it to navigation or site map yet) - so please be sure to bookmark it once you get there.
I will add more Droid wallpapers as I get them, or create them, and may start adding a few Motorola Droid or Google/Android-related news items as well. Don't know yet.
Anyway, enjoy: http://www.weedhopper.org/droid/