Texture
One thing that really ties together a level or character design is texture. This is the very reason textures are designed by human hands. They usually convey a specific tone. But one thing that we can use to our advantage is the fact that a lot of textures happen naturally.
This would be similar to the stripes on a tiger. Realistically, we wouldn't see a constant pattern around the tiger, though. We would have to break the tiger up into sections of texture such as, the most prominent stripes would be on the back and they would fade as it wrapped to the stomach.
One way to accomplish this is to have animals of a similar shape so that the texture map will apply similarly to the different animal models. The textures can be tinted in different colors so that the animal shape and color will stand out over the texture, which is more ambient. Also, making the colors of the texture similar will blend the texture patterns and make the...