You should think about composition as well. I’m missing a focal point. Right now my eyes don’t seem to find their way… donnow where to look first, if you know what I mean.
the skeleton on the right, having it’s head cut out of the image partly really disturbs me.
It’s good that you experiment with different lighting situations.
Think about where the light is coming from, why is it coming from this or that certain direction and not from another? Which elements in your scene will be affected by it?
For example, the chairs are lit from a light source coming from the viewers direction, but positioned very low, just above the ground. I think part of the skeletons should be affected by that same light.
It is always a good idea to plan your light sources at a very early stage.
Anyway,
there are a million things to say about using light.
There is a lot to find about this on these lovely forums. (use the search button
)
Also there are some interesting tutorials on www.imaginefx.com
Each and every one of them will talk about light at one point or another…
Hope this helps and you will keep pushing yourself 
greetz,
43