Nice effort, and potentially really useful and something i would pay for.
However, there are a couple of issues for me:

1. When pasting a PNG file containing text to watermark the image, i end up with some frames that have a thick white border bottom/left. Plays OK once i a delete those frames.
2. There should be more control as to where an image can be placed. Top/bottom/left/right is barely adequate.
3. It should be possible to scale the pasted image!

I'm sure the author is already working on these issues, and i will keep an eye on this software....