A Few Suggestions
Her are some suggestions:
A blur tool, some new brushes, a filters feature, blending modes feature (for layers) a symmetry tool, a magic wand tool, and to be able to draw outside of the canvas.
Sorry if I listed a lot of stuff and some very complicated things! It's fine if you cant add these things, but I'd appreciate if you could! I think this would be a very professional app if these things were added!