Reward Ideas for player creating a map

If you are currently going through the Blighted City, please skip this post.

So, my players are investigating a cursed city on behalf of a silver dragon, and at the start, I warned them that they should make an irl map in order to know where they are going and retrace their steps if necessary.
What I did not expect is for one of the players to start making a really beautiful, detailed map with illustrations and everything. He also said this is what his character is doing in-game as well, as he wants to try and impress the silver dragon (who basically raised him).

I really love the effort he put into making this, so I want to reward him appropriately. What should I give him? He is a level 7 Wild Magic Sorcerer. Also, I don't want to give him anything that has to do with Wild Magic because he already has an artifact that plays around with that mechanic. I really want to give him something cool, and I was wondering if you guys have any ideas. Thanks!