Oh yes, there is Otto in the handbook. I don't have it on me, as I'm at work (my boss is being a Mafia Don somwhere else today, so I have my peace to do one work-related item and one that I like in turn, like the proper BOFH that I am), so I can't say you on which pages; he is there remarkably more often than once. And he does look like Adrien Brody, especially around the eyebrows and nose.

Well, there might be some Margo in that Art of Discworld book that's being announced and postponed all the time...