The sequel to my code editor, this tool lets you view how watermarks will look on your art, without repeatedly uploading and regenerating like you have to on Toyhouse. If you find bugs, you can respond on the related thread. Hopefully that's a time saver for anyone who needs it. You can also use it to apply watermarks to art if you want to!
Just a few examples of the images it spits out (tile, stretch and center watermarks):