Problem with preferred watermark

A friend uses a translucent grid for a watermark and I really like it. Doesn’t intrude on the picture, looks good and would be very difficult to photoshop out. I just downloaded the VP.net watermark software and gave it a try. I had made a grid in Paint that would be large enuf to include a complete picture. The menu tells me that the watermark must be smaller than the picture. What can I do ??

Thank you

Lar.