I have spent a good amount of time trying to find each individual monster, and its far too much of a pain (not lazyness, just not enough monster sprites to reflect what I have in my D
I have conceded to the idea of having a single sprite but different colours roaming my world.
Basically the below (still to properly make into sprites, wanted peoples views first) have different colours.
I was either going to make the different colours difficulty for the fights for your level (so if a monster level is for 1-3, you are 6 it will be green "easy") or if you were 4, the monster level was 10 it would be red for "Hard" e.c.t.
That or just as monster packs are bigger / harder e.c.t. reflect with colouring (without checking your heroes level).