Well, April Fools or not, you're just continuing the tradition of special graphics levels featured in Lemmings 1 with levels like "A Beast of a Level". Some ports/editions of Lemmings 1 even have their own unique special graphics levels. The terrain for those levels are in fact stored as a single image, effectively a giant tile. Past fan-created game engines like Cheapo also had its share of this kind of levels (some are actually decent puzzle too IIRC), and NeoLemmix probably has a few as well.