I have tried several different types of editors for Terraria (more for the fun of it, I always do have a windows PC...)
One that did work for me is:
MoreTerra.exe - a map viewer generating a PNG pic file of your world.
I simply use the run command, using the Terraria bottle.
other editors listed on
http://wiki.terrariaonline.com/Map_viewers
did not work for me. There is a python world viewer which should work natively on osx, but it requires python 2.6.6 (I have 2.7.2) and won't install otherwise.
The TerrariaViewer for inventory editing didn't work.
Anyone else had any success with any external viewer/editor?