Simple suggestion, although I am not sure what kind of effort would have to be put forth to make this happen.
Whenever an object (resource node, mob, player) spawns or despawns, let this be done with some sort of animation or effect. As it is now, whenever these spawn, they simply appear or "pop" into existence. It's just my opinion, but if there were some sort of transition between these two states, I think it would be a nice touch; it take away a bit of the artificial feel the system has now.
The animations / effects needn't be overly exotic. Zombies, when they spawn, don't necessarily have to claw their way out of the ground. They could fade into existence, or perhaps appear out of a Blight ring (rather like the Hellspawn who teleport into existence in Doom3). Despawning could be handled in much the same way.
Just an idea, though, and I am certain there are other things that should be done first.