InjectedXna is a POC project for drawing in WoW using the XNA framework. The InjectedGame class attempts to mimic the XNA Game class, but uses the DirectX Device pointer of WoW for drawing.
Pretty hacky, not complete, and liable to break.
See samples/Primitive3DSample.sln for an example of using it with one of the default XNA samples.
View commit history on samples/Primitive3DSample/Primitives3D/Primitive3DGame.cs to see how it was implemented.