Fishmen - totally Deep Ones. And therefore awesome. Shadow Over Innsmouth and Thing on the Doorstep are two of Lovecraft's best.
Neandors - potentially interesting idea, wonder what was meant. Can anyone translate the latin/greek? Are these supposed to be Neanderthal "regressions"?
Catpeople - the latin name just means hairy, and the "Gothic" name is "Felinid", so could just be a very hairy human? Or perhaps something more monkey like, less catgirl? Though I think that the Catperson concept can be good - read the Instrumentality stories for some interesting catpeople.
Treepeople - I'm seeing this as less dryads, more as gene-engineered survivors with symbiotic plant life, similar to Orks... If anyone has read the Book of the New Sun, like the Green Man that Severian meets in the circus, like that.