Alright, not sure if this is possible, but just recently I was watching a video and it suddenly occured to me that we always see poofs of blood in the air, but thats it. So, why not have blood on the ground once an enemy has fallen dead?!
Basically, upon any death, at the end of the death animation, a pool of blood appears under the body. Now, this could be a growing type mesh that appears small and then grows to final size or mabe it just appears out of no where, or just use a texture animation with a single loop. I think the best thing would be to have several random types with just one appearing under a body to keep things from being too regular; if possible, also simply rotate the mesh randomly.
Now, we know that sometimes an NPC will die on a slope and lay flat there. So either the blood could stay with the NPC(it isnt getting anymore unrealistic anyway) or it could just detect the slope of the ground and match it closely.(if this is even possible)

So, any takers?

http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=797

Wow, I cant beleive I missed that. I literally went through as many mods on PES as I could at one point (which is most of them)and I am suprised I missed that completely.
Another great old mod.