Pokémon DS Map Studio and Spiky's DS Map Editor Spiky's DS Map Editor (SDSME)
do not allow the direct extraction of Official Pokémon Game Tilesets.
If you want to - for example - add a single house to a Route, you must recreate the entire map first.
That is why I will recreate some of Pokémon HG/SS's maps essentially Tile for Tile, before making my own real edits.
This is a Recreation of HG/SS New Bark Town in Pokémon DS Map Studio.
You may use this as a basis for your edits. You need not credit me, since this is merely something akin to 'Step 1' of the real work.
(I had intended to upload many more such maps, but I have decided against it for now, sorry )
Please inform me, if you see anything wrong (Those Grass Tiles ARE very small! XD)
If you are seeing this and want some resources:
MasterYesevil's DS Rom Hackiing Tutorials Thread
DS Rom Hacking Resource Collection Thread
Pokémon DS Map Studio + g3dcvtr (paste these files into DS Map Studio's bin file)
Spiky's DS Map Editor (SDSME)
DS Pokémon Rom Editor (DSPRE)