The best advantage of a GUI based utility for this would be real-time preview. You put in your tile definition and a few settings and see the preview results instantly. That would really help make it more intuitive.
Yea, in that format, besides sometimes it is hard having to figure out the more sophisticated type graphics that use Fixed Width would do very well, I mean we do have Crystal Tile, Tile Layer Pro, Tile Molester, and of course YY-CHR that are of the standard stuff, but we all know about those things, well maybe not so much for Crystal Tile since it is made in China, but also recently discontinued support for Windows 2000 and Windows XP since it is hard to keep maintaing it.
Besides that, it would also be good to have an added clipboard function so that if you have one of the 4 programs above or a Paint program, it would make it more easier to transfer stuff to that.
Then again all of these are just my thoughts on the subject anyway.