By loop, i meant interconnect the end sides of the map either horizontal or vertical to be seamlessly connected to the other end for things like entities, walls, projectiles, movables, and most importantly, visually. Other than looping, I would also like to suggest displacement of the loop so that when you loop from the bottom left, it's possible to go "around" to the top right side of the map.
In pb2, map makers would just teleport the character from one end to the other with an imitation landscape on both sides but it's more like teleport area than an actual loop.
I guess rather than an entire axis, you could have sections of it instead and have it connect to another place probably without inverting it to create a seamless portal from one place to another but it's probably gonna be difficult. This is probably confusing to see visually too unless you covered the area around the portal with walls.