These are the most common ways that people create tile sets - either all jammed up together or with little spaces separating them out, and GameMaker Studio 2 can handle both types. Essentially all tilesets must be comprised of images that fit within a clearly defined grid, with each cell of the grid being the exact same size (note that while the images shown above are all made up of square tiles, a tile set can be made from rectangular tiles too). When creating your tilesets, keep in mind that the top left grid cell must always be empty as this is the tile that GameMaker Studio 2 will use for "empty" tiles in a room and for erasing existing tiles (and even if you have pixels in that part of the image they will be ignored).