As it stands, it's a bit hard to picture the depth of the stony floor
Surely this isn't an issue when it's moving though? Personally, I quite like it without major shadows, that's just MHO of course.
When the camera rotated around, the characters turned in little jerks and it was really off-putting.
The effect I was thinking of is more like paper dolls - in the Thomas and Nardo cartoon, people seen from the side looked flat!
I'd suggest going down the toon cel shading route.
But realistically, so would I.