Prerelease Maps
There are even more unused maps in addition to the early Tadpole Pond I discovered. As with that map, these were discovered using Lazy Shell. The code tags denote the settings required to view these maps in the editor.
Test Map

This map is a simple rectangle featuring 5 exit paths, 2 raised platforms, a patch of dirt and what currently appears as part of an Item Shop sign. Judging by the tileset, the latter was originally a different 2x2 object. The item shop sign merely occupies the bottom right tile.
GRAPHICS SETS:
GFX Set 1: 16 (House exteror)
GFX Set 2: 1A (Town Decor)
GFX Set 3: 17 (House doors)
GFX Set 4: 2F (Town cliffs, stairs)
GFX Set 5: 0 (NONE)
TILESETS:
L1 Tileset: 4 (Towns 1 (L1))
L2 Tileset: 5 (Towns 1 (L2))
TILEMAPS:
L1 Tilemap: 0
L2 Tilemap: 1
**No Physical Map exists for this map**
PALETTES:
Palette Set: 3 (Rose Town)
Mountain Areas (2 levels in one)

This group of levels shows that the significant changes were made to the Mountain tilesets. Many of the tiles in the tilesets were shifted around (and in the case of the signposts, removed), so there are many glitched or blank tiles.
The Super Mario RPG preview article in Nintendo Power Volume 77 (October 1995) had a screenshot (see left) of the first of these two areas. Everything but the grass in the bottom left corner of the image matches the ROM data, suggesting that the map was altered prior to being removed from the game proper.
Using this screenshot and the placement of the blank tiles in the tileset, I partially reconstructed these maps. (click the link for an image)
The sign graphics in the mountain tileset no longer exist, so I used Star Hill's as placeholders. As for the blank 2x2 squares on the bottom map, it's possible that the numerous rock piles seen on the floor in the 1995 V-Jump Festival version of Moleville once occupied these spots.
GRAPHICS SETS:
GFX Set 1: 33 (Shacks)
GFX Set 2: 1A (Town decor)
GFX Set 3: 0 (NONE)
GFX Set 4: 34 (Mountain)
GFX Set 5: 35 (Mountain decor)
TILESETS:
L1 Tileset: 19 (Mountains (L1))
L2 Tileset: 1A (Mountains (L2))
TILEMAPS:
L1 Tilemap: 2A
L2 Tilemap: 2B
Physical Map: 29
I could go into elaborate descriptions for the remaining maps, but I'm too lazy to do it at the moment.
I'll just give you the images for now:
Map 02: Town (exterior) (tilemaps no longer exist)
Map 04: Alternate Mushroom Kingdom (exterior)
Map 0A: Alternate Mushroom Kingdom (house interiors)
Map 10: 3 Sewer areas (tilemaps no longer exist)
Map 15: 4 Forest areas (collision data no longer exists)
Map 25: Bowser's Keep area (graphics/collision data no longer exist)
Map 26: 4 Bowser's Keep areas (graphics/collision data no longer exist)
Map 28: Town (house interiors, probably corresponds with Map 02) (tilemaps no longer exist)
Map 2B: 4 Bowser's Keep areas (same tilemaps as Map 26, graphics/collision data no longer exist)
Map 34: 4 Grassland area with 3 square shadows
Map 3A: 4 Cave areas
Map 3C: 2 connected Grassland areas with glitched pipes
Map 48: 5 Mountain areas (tilemaps no longer exist)
Map 4D: 4 Sewer areas
Unused Palettes
There are other unused monster palettes aside from those seen on the unused monsters:

Even the first form of Smithy has one!
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