OpenGameArt.org (OGA) has a lot of assets available for gaming [0]. In particular Kenney has loads of 2d and 3d assets that can be used as the basis for a wide array of games [1] [2] [3].

OGA has many Zelda-like tilesets. Some of my favorites: [4], [5], [6], [7], [8], [9], [10]

Also note that there's a FOSS Zelda game engine called Solarus [11].

[0] https://opengameart.org/

[1] https://opengameart.org/users/kenney

[2] https://www.kenney.nl/

[3] https://twitter.com/KenneyNL

[4] https://opengameart.org/content/overhead-action-rpg-forest

[5] https://opengameart.org/content/zelda-like-tilesets-and-spri...

[6] https://opengameart.org/content/16x16-game-assets

[7] https://opengameart.org/content/rp-destiny-sprites-and-tiles...

[8] https://opengameart.org/content/zoria-tileset

[9] https://opengameart.org/content/gameboy-tileset

[10] https://opengameart.org/content/forest-tileset-new-and-old

[11] https://www.solarus-games.org/

Solarus looks utterly amazing. Thank you for directing me to that. LUA, too! So easy!

Thank you :-)

Don’ let that stop you! There are a ton of free assets both for Unity and Unreal. Check out e.g. the free category in the Unreal marketplace.

https://www.unrealengine.com/marketplace/

Search for the RPG category. There are whole RPG systems you can plug into Unreal which you can buy for laughably little money. (No affiliation, I just like what Epic is doing with the engine)

Oh, I know! I have a tonne of assets already. They just all feel disjointed and I'm bad at lighting :P