@DerpyFast
For extra speed you can chunk static tiles at the beginning. Maybe like 512×512 but your chunk size should be a clean multiple of your grid size.
Even for this auto tile you can rotate the entire sheet to animate it.
You probally don’t even need graphics optimization at this point. From here I’d investigate more procedural generation, including automatic variations in your auto tile.
I love Gamemaker, but it’s been a while since I did anything big.