So, we all know what Rapunzel's art looks like.
But the longer I think about it, the more I think that the closing credits are supposed to be specifically Eugene's art style. Let's start with the map:
It's sparse, not too detailed, and includes things like a picture of Maximus labeled with "avoid this' and an arrow in the ground labeled "got shot here." If it was a pre-existing map, he'd have more pictures of trees to contend with, not a piece of parchment that's clearly being filled in as it goes.
Also, the art during the credits are all things that he was present for or knows well, even if he wasn't involved.
There's even a few things that didn't make it into the movie!
So given this, I say that if Claire Keane is the official artistic hand of Rapunzel, Shiyoon Kim is the official artistic hand of Eugene Fitzherbert. (And that the series blatantly got wrong/is not canon-compliant with how well he draws.)