I have a bad habit of filling in crowd scenes or secondary characters with comic book people, and Red Goddess is no exception. In the final book, only Alexandra (in red) is at full colour, everyone else is desaturated. Also, there are word balloons that cover some people up.
From left to right (in the background)
Michael Golden, Mike and Laura Allred, Gail Simone, Frank Miller, Lee Van Cleefe (not a comic person, but cool and in context with the western-y aspect of the planet) and John Byrne. Also, Adam Savage (of Mythbusters fame, and a huge comic bok fan) makes an appearance on the same page.
There'll be more crowd scenes later so expect to see some other comic book luminaries.