Gotta agree with Rick (BTW, it's
askew 
)
The way the StuG is pointed, it draws the eye right off the dio. Also, you have a huge "dead area" (empty) in the upper right of both bases. Either would work with a bit of dynamic composition.
Composition is a tough thing to learn unless you've had some artistic training or experience. Both Rick and I have newspaper and other publication experience, so we notice stuff like this. If you get a copy of Shep Paine's "How to Build Dioramas," he gives a pretty good run-down on composition.