My B3D is a bit rusty, but i think you can...
create a sprite (i think they're called sprites, the 3d billboard things under the 3d commands) with your image. Parent it to your camera. Set the entity order of the sprite so it is always rendered behind everything else.
create a sprite (i think they're called sprites, the 3d billboard things under the 3d commands) with your image. Parent it to your camera. Set the entity order of the sprite so it is always rendered behind everything else.