I started messing around with the idea of using a torus for a traditional hobbit door. This gives good results:
85% Hollow
Twist Begin 90, End 90
Hole Size X 100, Y .20
Profile Cut Begin 0, End .550
Size X 1.5 Y 2.0 Z 2.0
Rotation X 180, Y 0 Z 180
You'll get something that looks like it has both a small knob in the middle of the door, and a slightly raised rim.
Texture all around with an appropriate wood texture, and give the "back" of the prim a slight gray coloration. You'll see that the "recess" behind the knob on the front also turns that color, giving focus to the knob. You can also texture the rim, so that the front of the door may appear to have 3 separate textures.