As you are modeling don't be afraid to deviate from the original design, this kind of free flow will make your model realistic. You can use textures to create complex looking geometry, far more efficient than creating the same effect using actual geometry. The best way to create textures is to again, refer to the real world. Take a camera everywhere and use these images to create your textures. If you don't have a camera, then do a search on the internet.
Photo reference is great for seeing how things look.
Also your limitations apply just as much here as in the modeling, knowing what size of palettes to use and what colors to use is vital. The texture is more important than the mesh when creating an emotion for the character, as it can create the fine details that wouldn't be possible within the mesh. Animation Animation gives the character life, so it must be accurate and, most importantly, capture the mood. Its extremely difficult to create a humanoid animation from imagination alone so again, use real world references, watch how people move and the subtle movements they make, this makes the animation believable. Even when not doing humanoid movement it is difficult to imagine so it sometimes helps to act out the animation yourself.