Be like Super Mario Bros. 3 where there's a world of every kind: ice world, grasslands world, forest world, mountain world, desert world, water world, lava world, sky world, giant world (this'll be hilarious), pipe world (maybe make it tunnel world instead), and demon world. Maybe add in urban world and swamp world too, while we're at it. Then to add even more worlds, make lava mountain world, giant water world, demon forest world (watch out for the tentacled things!), icy sky world (constant blizzards with winds of 60 mph will be your standard forecast, watch out for the ledges), and other combinations.