Starcraft 2, like it's predecessor before it, has a very robust level editor called Galaxy Editor that allows you, the DIY modder, to create nearly any scenario within the bounds of the Starcraft 2 engine that you could imagine. We have compiled videos on how to do all sorts of fun things with it, from making RPG's and Tower Defense games to just making you dream Starcraft 2 level. This video will teach you how to import custom 3D models into the Galaxy Editor and then use them in your custom maps. You can't animate them yet, but they work great for making static map elements that will make your map stand up.
Download the models used here here.