How tiles images work - the rule sets are the material configurations but I can't say that's a super simple subject. The rules can look at what other tiles are around. Any tile at all, the same tile, specific materialIds, etc above, below, to the left, to the right, diagonally, 2 to the right, etc. That's how it knows where to place borders, corner pieces, shadows, etc. You'd definitely need a new one you cooked up. I'm not sure exactly what you have in mind, but it might be far easier to place objects that are 2x2. Objects can themselves place tiles, but generally for collision purposes they place meta-materials like invisible solid blocks, invisible platforms, etc. Then they have their own image.