First thing off the bat was making the creatures have some sort of logic to guide them. I've started to split things up into different logic flows. For example, in the screen above, things are "territorial" meaning they will wander about near where they spawn, but if they get too far from that point, they'll rush back to it. There's logic for Aggressive and Passive creatures in early stages too - but what this is letting me do, is slowly develop more interaction types and consider how they might allow me to make the game more interesting. One certain thought is that one monster could alert others nearby if being attacked or attacking. I might set up monsters to have affiliations - so they might even fight one another in some cases.
I've also fixed up the code so that monsters follow the same rules as a player when they walk about the place - so no more place-holder monsters that could walk over anything they wanted. I'll keep adding and tweaking until I am happy with where this part is, then I'll solidify that into an editor interface to make this part of the encounters/monsters and shift to make the true combat aspect.