Low-poly modelling and rigging. – For people with less advanced PCs or for assets in MMO environments.
Isometric rooms.
Simpler objects, like bottles, cans, lamps, I feel like there is a slight lack of easier material. Maybe course on a small set of props that could be used over and over.
How to LOD your model.
Texture drawing – Like making wood, rock, seamless textures in Photoshop or Gimp, making normal and specular versions of them, (understandable if you’re not looking to cover this.)