Thanks eishiya, you're definitely right about the contrast.  It looks much better with the purple color.  I will update it after the voting period. 

So cool. Reminds me of Castle of the Winds.

The dark pattern on the floor blends with the characters' outline colours and makes them more difficult to read, and the high contrast makes the characters stand out less. Consider replacing the black floor pattern with the purple colour, like this.

I think with the contrast problem fixed, your existing tiles look quite good! More diversity could help, but it isn't necessary.