Changing Terrain tile sizes??

Is there a way to change the density of the art tiles sizes on the terrain. I cant seem to find where that would be in the editor. I tried making larger tile art 512, 1024, etc. and it doesnt seem to change the resolution it just does some kind of wierd stretching routine on a single axis.

I want more resolution from the tiles.

Anyone know where this can be done? can this be done from the editor? or is this a code change?

thanks

- M