Somehow, yes, but it is quite limited.
Standard loadscreens are indeed 3D files that contain only textured planes.
The camera looks down on an area going from (X=0,Y=0) to (X=0.8,Y=0.6), without any perspective (Z coordinate has no influence, except if you want to superpose different meshes).
There is also no lighting by default, so you have to either make your material unshaded, or add lights inside the model.
The model will stay unanimated during loading, and will play its Birth animation when loading is finished (including particles).