[Plugin: NextGEN Gallery] Custom image watermark

Hello, I installed this plugin today, simply awesome 😉

Just one thing I cant solve… I need to add a custom watermark image, I have it on my server both in gif and png format. In watermark options, I set the full url to the image (with http:// etc) and save the settings.
Already tried with local path to the image too.

Then I go to “manage gallery” and I select “set watermark” and I get the message “watermark set for X images” but there is no effect in the images.

If I use the text option for watermark, everything works, but with custom image doesnt.

Any clue?