Layout and Presentation
I notice a distinct lack of 3/4 views in your sheets. While front/side/back might get you a technically accurate 3D model, an angled view will exponentially help get across to the animators/modelers what you had in mind for the design (trust me, I speak from experience). I know some studios will let you get by without doing a 3/4 angle, but the big studios require a higher standard. Check out some Disney model sheets if you can find them. I'm pretty sure you can find a few online, or maybe someone here can hook you up. I don't have the ones I worked from, or I would show you. Also, Every pro model sheet is going to have some text information: Name of the character, Project they're associated with, Relationship to the main character, etc. With yours, I might actually give an evolutionary description (reptilian, amphibious, mammalian, avian, etc.). You could even get creative and give them a binomial nomenclature in Latin. I do want to say that I really like the head views in the sheet for the dark skeletal girl. An animator/modeler would really appreciate that level of effort.