SO! To get started I have an influence map for my spiteful plant woman:
(I had to shrink it a little so sorry if it's not the best quality)
There's still a lot of indecision at the moment towards how she'll actually end up looking. I plan to create many different versions of her before I decide how she should finally look and I'm already working on the head shape in my sketch book, so expect the scans soon!
This is the general plan for all the characters I want to continue with, and any others I come up with later. Experiments, tweaking, defining and then polishing (maybe followed by a bit more tweaking). Roll on experimentation! :D