They look pretty good. I can tell you had fun making them and that is important.
In your color images maybe the darks of the shadows could be cooler, and a bit lighter to show off the detail, like an illustration. You could also warm up your light source a bit.
I dont know how to do that in 3d, maybe some kind of second light source or ambient light. But this will help it look more like a colorful illustration that reflects the mood of the characters you have designed. Which is "fun" shapes!
The harsh shadow I think takes away from that in the color version. They feel more serious and gothic and diablo 2 in that regard.
If that is like an ad, or the thumbnail for the figure print line or something, I would want it to be colorful and fun and prismatic so people would want to click on it.
Look up a color pallet to try to match the fun feeling.
Hope that helps. Keep having fun.
