Watermark on one image only

Hi,

Tried searching with no solution found. I have been running Gallery for years and had no success doing this and I am moving to a new hosting provider and upgrading to Gallery 3.07 and saw I cannot do in that version either.

What I need to do is add a SALE watermark or banner to the main album picture on one album only. For example: I have a Gallery of say 9 items and I want to have the SALE banner/watermark on two or three of the Album covers and then next week change it to a different two or three. Basically editing the pictures and adding the watermark/banner to the picture then uploading it again is not an easy option.

Any help/advice appreciated. If it can't be done then I may have to look at other options.

Thanks