This is a full list of the levels included in the game, along with their creators.
World 1 - Green Grass Gradation
Wood in World One (Deckiller)
Green Goomba Hills (ShortStar)
Green Greens (AncientNoob)
Pondville (Link_2112)
Giga Underground Way (Gigabowser)
Creation Alpha (Deckiller)
Supra Mairo Bors: Boswer's Castl (kentona)
World 2 - Vegetation Agitation
Green Suede Shoes (Solitayre)
Picky Picky (halibabica)
Ghost Circle (Racheal)
Castle Notsobad (Isrieri)
Supra Mairo Bors 3: Pippes (kentona)
Woodcutter Castle (nin8halos)
Piranha Palace (Solitayre)
World 3 - Trouble Town
Supra Mairo Bors 3: Agnry Sun (kentona)
Underground We Go! (narcodis)
Sunken Desert (Solitayre)
Supra Mairo Bors 2: Dessert (kentona)
Lakitu's Playground (Ratty524)
Batty Bungalow (UPRC)
Koopa Bros.' Tower (Desmo360)
World 4 - Peaceful Rest Vacation
Crabby Coast Crossing (UPRC)
Kentonee Floodplains (kentona)
Starlight Lagoon (Solitayre)
Ghost Wall (kentona)
Oasis Ruins (Deckiller)
Ruins of Muda (nin8halos)
Mairo vs. The Tree Baes (kentona)
World 5 - It is Very Cold in the Sky
Crystal Forest (Solitayre)
Precarious Platforms (GreatRedSpirit)
Supra Mairo Bors 3: Clowds (kentona)
Ghost House Blues (Desmo360)
Supra Mairo Bors 2: Whale Whale Whale (kentona)
Frosty Tower (nin8halos)
Mr. L (halibabica)
World 6 - Bowser's Sauna
Supra Mairo Wrold: Crush Cavs (kentona)
World of Hurt (halibabica)
Triad Airship (Deckiller)
Blood Ocean (nin8halos)
Crimson Slipper (halibabica)
Fortress Aflame (nin8halos)
Bonus Stages
Good luck finding these! They're all top secret!
Skull Lake (Davenport)
Lakitu Bros. (halibabica)
Coffee and Donuts (nin8halos)
Crystal Cave (Desmo360)
Snowy Spiny Summit (UPRC)
Supra Mairo Bors: Lost Leevls (kentona)
Great Palace X (GreatRedSpirit)
Mario in Heat (nin8halos)
Eli's Fortress of Doom (halibabica)