The blender model has to have the texture as an UV map (just like here). Make sure you have it well configured (if you pack the textures in the .blend you should see it great when just loading, wtithout the need to specify the material and texture by hand, if not, something is not well done on blender); the mesh should have a buffer with the tex-coords (to check this use: geom.getMesh().getBufferList();).
Once you make sure you know how to let it ready for jme3 in blender, you can try to set the stencil again.