Vitor's Mode 7 mapping tool, released in his Ultimate Tool Request thread from Winter 2019.
You can utilize this to edit tilemaps to look how you want them to look in-game, and you can also project the tilemap and preview how it looks after a matrix transformation. Lastly, with some C# knowledge, you can also create a custom projection.
For use, convert an image to SNES 8bpp Mode 7 using SNESGfx, with tilemap, and upload it to M7 Map using the open options. From there on, it should be simple. Easy Mode 7 Patch required if you want to use it in your hack, of course.