Making an unbuildable texture?

My problem is pretty simple: I need a grass tile that is unbuildable.

The easiest way to solve this is probably to just edit the pathing map. I don't know how to do that though, so I'd be glad if someone could explain it to me. :)

In my opinion a better way would be to have a custom tile that is unbuildable. I'd prefer this way so that I could use this tile whenever I want without worrying about pathmaps. Is there a way to make such a custom tile which would show correctly on everyone's computer that just has my map?

I don't know about custom tiles, but Ashenvale and Felwood have a "Vines" tileset which is unbuildable and looks kinda grass-like. There's also a "Crops" tile in the two Village tilsets.

--general "nihilist" mx

To edit the pathing map dl zepir's editor (from here) and edit it. If you do anything strange the WE will reset the pathing map to the default when you open the map in it, so do the pathing editing at the end.