Interesting thread.
This is good actually, gives me some ideas. I know these are all totally hypothetical, but I would like to note that I won't be doing any portraits that Sideshow currently has a direct license for (that I'm aware of). I don't want to step on any toes as you can understand. This means no Star Wars, LOTR, etc. In fact I wouldn't have even released Craig if not for the fact I was left with the sculpt after a private commission fell through.
That said, a few likely subjects might be (in no particular order):
1. Russell Crowe
2. Clint Eastwood
3. Ian McShane/Swearengen (good call Psycho!)
4. Nathan Fillion (in progress)
Also, there is another head already in the works, commissioned by a fellow board member some time ago... I'm not sure if he wants to make it public yet or not, but I'm sure the actor will be on many folks' lists.