Tools
Gamemaker studio
GraphicsGale
SFXR
Audacity

I also might be using an autotiling script that I wrote during the last miniLD I entered. Those scripts, along with an example on how to use them, can be downloaded here:
http://www.jajaben.com/LDExample.zip

(I’m not claiming these are well-written/efficient. I’m not a programmer. I’m just saying I might use them, and that’s why I’m sharing them)

If you use this tileset as a base, import it into gamemaker as a sprite (create from strip), then delete the 6 black squares, it should work then.