You should be able to just change the TS macro to 16 to use 16x16 tiles but you have to be aware of the limitations. All objects colliding with the tileset will need to not have collision masks bigger than 16x16. If you do have bigger masks, say a 24 x 24 for example, you can imagine if you have one tile and the instance trying to fall onto that tile, because we check for a collision on the 2 corners of the mask, it will simply slide over the top of the tile and not collide. If you want bigger object masks you will need to add an additional collision check for the center of the mask horizontally and vertically using the same format as the ones I've used.