Wish I had found this a year ago... lolAnyways, It has a nice layout to it, just load your tileset you want to mod on the left...
(Yes I know it's in German, cant you discern what is what from the icons?) And load the tileset you want somthing from on the right...
(Oh common... you do know your left from your right dont you?) Click the square on the right that you want and click where you want it on the left. Then click the save icon and enjoy...
(Oh I suppose it has other uses...) Enjoy!!!
Here is the screenshot...
Here is the Download...
**EDIT**
I added a screenshot for you guys/gals/paedobear lovers.