The concept itself is nice and you are on the right track so far as placement and balance is concerned.  But it does however look a tad flat without any depth because there doesn't seem to be any shadows.

If you are using IBL lighting, it doesn't cast shadows.  You will have to add an infinite light or two to the scene for shadows to be cast.

Lighting is a really hard concept to try and learn in Poser. It's really advanced.  If you are using Poser 5, a good lighting scene can take up to 20 or more lights to place around the scene.  With Poser 6 and Poser 7, you don't need as many lights, but the IBL and AO gives it a whole new set challenges.

My advice to you as a new user to Poser  is to go to RDNA and download some or all of their free light sets in their free area.  They have lots of great lights and they all work very well in Poser 5 and Poser 6. I use them quite a bit myself.

http://www.runtimedna.com/mod/forum/

Once you have some shadows in that picture to provide some depth  that will be a really great image :)

EDIT:  A nice creepy background picture behind would be a nice addition too.

You can find lots of free backgrounds in this thread:

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2678784

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi