Anything from Leader Games and illustrated by Kyle Ferrin (Root, Oath, Fort...) feels like cheating but still, I absolutely adore their art style
Everdell, Photosynthesis, Parks, look nice as well
I also bought an updated edition of Costa Ruana just because of the illustrations: https://www.pamwishbow.com/client-work/project-four-yjynj-pafyx
I'm right on board with you with Kyle Ferrin. I've spent... a lot of money on Leder Games games.
It's interesting how Kyle Ferrin managed to develop such a unique, recognizable and charming art style that I when I looked at OP's picture, I instantly thought "huh, the art style of the third board game reminds me a lot of Root"
Yeah it's Oath, I bought it, I don't even know if I'll be able to play it with friends, but I need all the Kyle Ferrin I can humanly collect in my life. His cute critters and goofy faces and lovely sketch lines and textures are just so adorable
Edit : btw I stole the pic from the first image search result I could find that showcased nice looking games, it's apparently from this article : https://gamerant.com/most-beautiful-board-game-boards/
My first thought was "I've got to share about Root" and then looked closer and thought "they probably already know"