well idk about photoshop tileset making, but what i do for my iso tilesets is
1. get a template of a tileset (the file with the 2 colors that go 32x32)
2. make the shapes/outlines of the things i want on the map
3. dunt put them together! so u can use it differently
ex: windows and a wall
- make the windows on a diff spot with nothing surrounding it, then on the wall
- leave the wall blank with nothing on it besides its color
4. shade!
ot much kinda same thing as normal tilesets to me