Hey, I found something out and I figured I could be helpful. We don't have a list of the possible shapes for tiletypes, but it can accept a number as an argument; and this means if you input "paint sh 1", it'll accept that and you'll see that it changes its shape to "WALL". So you can use this to probe around and find the names of the constants it'll accept.
I've made a list of shapes and what it paints. But first, some notes:
Just using shape without defining a material (or sometimes, the material without defining the shape), CANNOT change a tile into something that the material can't be (for example, you can't turn floor fungus or soil floors into walls or boulders, and can't turn trees into walls made of wood). If you want to change floor fungus into a wall of solid rock, you'll need to both set the material and the shape in one go. Otherwise the tile simply won't change.
Also, the SPECIAL state will be preserved if possible (the SPECIAL state determines whether something is smoothed, furrowed, a river source, etc.). For example if you use a WALL shape on a smoothed FLOOR, it will turn into a smoothed WALL.
You can use -1 to reset any of the options. (e.g. paint sh -1 will remove the SHAPE setting)
0: EMPTY <Empty space; only works on tiles that are a form of empty space, e.g. a downwards ramp>
1: FLOOR <Cavern floor; this will effectively mine out wall tiles. This covers both smoothed and rough stone>
2: BOULDER <Creates a rock boulder, e.g. the kind you see on the surface and can only remove by smoothing; seems to set the tile as smoothed>
3: PEBBLES <Can turn stone into a floor tile named '(material) pebbles'
4: WALL <Turns stuff back into natural walls, can be smoothed or rough. Note that smoothed walls will not automatically connect with each other, and thus you can get pillars adjacent to each other>
5: FORTIFICATION <Turns something into a fortification, and sets the tile to a smoothed state>
6: STAIR_UP <Upward staircase, smooths tile>
7: STAIR_DOWN <Downward staircase>
8: STAIR_UPDOWN <Take a wild guess>
9: RAMP <An upwards ramp; does NOT change the tile above it>
10: RAMP_TOP <Downwards ramp; can only be used on empty space>
11: BROOK_BED <Only seems to work on water, appears to erase the water; I can't figure out what it does but I assume it has to do with brooks>
12: BROOK_TOP <Only seems to work on water again, can't figure this out, erases water>
13: TREE <Only works on vegitation, creates a tree out of the selected plant material, even shrubs! You can have wild strawberry "trees", not sure what happens if you cut one down though. The vegitation maintains its alive/dead state, so creating a tree out of a dead shrub may leave you with a "dead longland grass" tree, for example. This can be used to insta-grow saplings>
14: SAPLING <Vegitation only, turns it into a sapling of the given vegetable>
15: SHRUB <Turns vegitation into a shrub of itself, again it even works on trees>
16: ENDLESS_PIT <Creates a chasm out of empty space, just like the one in Arena Mode; amusingly, you can create one in midair several Z-levels above the ground, I guess it creates a wormhole or something... Combine this with the HFS material to create an eerie glowing pit!>
And here's a list of materials, which can allow you to set things specifically and for example, turn a rock wall into a wooden tree or empty space. Some notes first.
It doesn't seem possible to define a specific material; whatever world you're using appears to have the materials of any given location on the map hardcoded, e.g. based on the veins and stone layers. So you can't just create admantine out of thin air, but you can use this to replenish mined-out veins. (paint sh WALL, paint m MINERAL)
0: AIR [Used for downward ramps, EMPTY, chasms, and so forth.]
1: SOIL [Silt Loam, etc. Seems to turn dead floor fungus into furrowed silt loam]
2: STONE
3: FEATURE [Admantine veins; you can't use this to create admantine just anywhere, if you attempt to, it will show up as 'unknown material'. It can only be used thus where an admantine vein is present]
4: LAVA_STONE [Creates obsidian, independent of the layer stone]
5: MINERAL [If it's part of a vein of non-layer stone (e.g. microcline), it'll turn the stone into that mineral, otherwise it'll just turn it into the layer's stone]
6: FROZEN_LIQUID [Creates ice, but it won't freeze water...]
7: CONSTRUCTION [Doesn't seem to work, but if used on floor fungus, creates "Muddy Floor" (Yes, the material is blank and that's two spaces)]
8: GRASS_LIGHT [Allows you to make grassy floors (or fungal floors in caverns)]
9: GRASS_DARK [Same, except the tile is colored darker than GRASS_LIGHT]
10: GRASS_DRY [Same as above, except it says "Dry (grass type)"]
11: GRASS_DEAD [Same as above, except dead]
12: PLANT [Only used for trees and shrubs]
13: HFS [Creates 'glowing floors', walls turn into 'glowing barriers'. Use this with the CHASM shape for an Eerie Glowing Pit.]
14: CAMPFIRE [Creates campfires out of floor tiles; described as 'ashes']
15: FIRE [Creates burning floor tiles; described as 'ashes']
16: ASHES [Creates ashes, which have the same icon as spent arrows]
17: MAGMA [Semi-molten rock and magma flows]
18: DRIFTWOOD [turns the ground into 'driftwood', which has the same tile as bars]
19: POOL [Creates murky pools]
20: BROOK [Only placeable on water, seems to replace it with Brook tiles... I think now that this is what the BROOK_TOP shape is for]
21: RIVER [Creates waterfalls and rivers; it created 'waterfall' tiles when I used them on mossy cavern floors, 'river' when I used them in underground cavern lakes]
The following SPECIAL values can be used:
0: NORMAL <Nothing special about this. You can use this to unsmooth stone though>
1: RIVER_SOURCE
2: WATERFALL
3: SMOOTH <Works on walls and floors, determines whether it's smoothed or not>
4: FURROWED <Makes a floor furrowed, e.g. after you build and then later remove a paved road>
5: WET
6: DEAD <My guess: Controls whether trees and shrubs are dead or not>
7: WORN_1
8: WORN_2
9: WORN_3
10: TRACK
Not sure what all of them do, but this is at least a good list of values you can use.
Other information: If you turn walls into empty space and it leads into unexplored territory, that unexplored territory will only be revealed when the map is updated (e.g. you dig out a tile somewhere nearby).
I hope this information is helpful, and hasn't already been posted somewhere.
Knowing how this tool works is vital if you accidentally use liquids with the of (obsidian floor), set on block mode, and wind up accidentally paving over your magma smelter's magma-hole... like I did. That said, have fun rewriting your world.