Long Face Ash has never been far from my radar. But sometimes I'm not sure what I feel like designing (or polishing to completion) next. And sometimes all it takes is to read one request in my email or on this forum, and then I say... "Ah, let me try that right now, what the heck." And sometimes it clicks.
Someone recently suggested Christina Ricci as Wednesday Addams. I thought, "Would that be easy to do? Hmm, let me just try real quick...." BAM. Done.
Ajax, every other idea you mentioned is high on my hit list. It's baffling to me how I some characters continually get left out. Every year I think, "This is the time for Vader and Predator and Hitchcock." Then somehow it's Halloween and we're saying, "Maybe next year."
On the bright side, it's it nice to know that there are still popular and in-demand ideas still to be done? That means we have some exciting pattern launches and show stoppers for upcoming Halloween seasons. It would be sad if we ever got to a point where we were saying, "Oh well, everything cool and popular has already been done."
Although, even if that did happen, then I'd just start over and make a newer version of every single character.