As long as you've drawn them yourself it's ok, by "unique" I just mean that they haven't simply been found on the internet.
There's some pretty simple cartoon-style drawings:

or some are a little more detailed:


but as long as they're in colour, unless the monster suits it if it's a shadow or ghost etc, it should be good. These are the lower level monsters though, some of the ones missing are dragons, devils, minor deities, wyverns and other more interesting creatures like that.
The only decent character class drawing is this one I think, the Ranger (you don't see these pictures as much though, they only appear in your profile):
