You can try it here ->
What do you think?
I would have liked to know more about normal maps and that kind of thing to make the “painting” look more real, but I am happy with the result.
I also wish I could show the inside of the mouth in dark mode, but I don’t know how to do it (Not even if that’s possible)
I like it! Great job 
Normal maps are used to fake depth on a 2D model, it allows you to have bumps and the likes without actually modelling it on (reducing polycount and weight of the asset as a result). You can generate them yourself, for example like so :
You could potentially darken the inside of the mouth by putting a facemesh with the mouth toggled on under your mask facemesh and darkening that one.