Hi! Thanks for spreading the word about Sprytile.
I'm not very familiar with where to get tile sets, unfortunately. If there's a specific game with tile sets you're interested in, you may be able to find them on Spriter's Resource.
Here on itch.io there are some asset tags you might like to explore.
https://itch.io/game-assets/tag-tilemap
https://itch.io/game-assets/tag-tileset
I'm not specifically endorsing these assets, but they look like they would work well with Sprytile's workflow.:
https://cuddlycolin.itch.io/desert-oasis