In terms of readability I do like Lazycow's edit, but for a game I feel this could all be perceived as too harsh on the eyes. The contrast with this is too extreme in my opinion but you definately could push the values more without loosing too much atmosphere. It is definately a stylistic option but with higher contrast you've sacrificed your control of saturation.
The motivation behind my edit was more to push you in the right direction as I didnt want you to stray too far from what works with your original concept, I feared too much of a radical change could put a huge spanner in your works.
Here I've made another edit to quickly to illustrate if you did want to inject a tad bit more contrast into this without sacrificing too much atmosphere,
(MEGAQUICK EDIT)

Also to distinguish the sprites a bit more, you could give your sprites a particular colour variable, I've also outlined your sprites.
Hope this helps you out.