Amazing!! The only critique that I can give is that maybe you could work on your anatomy a bit more. I just think it would really bring these guys to life! (more so). I went to Wellington recently for a workshop taught by some of the guys at Weta. They said that this is the best anatomy book: http://www.bookdepository.co.uk/Strength-Training-Anatomy-Frederic-Delavier/9780736092265It isn't an art book but it has loads of breakdowns and detailed drawings in it. Hope this helps!
You are absolutely right Pete and thanks for link!
I love your creature design, looks awesome man. Especially the first one. I think my critique would be also to maybe avoid the symmetrical pose on few of the characters. They look great tho!