I found that I had to crop the part of the image I wanted, as the scanned image itself included a lot of empty space. I also had to reduce the size of my scanned signature a lot to fit it in the box...to about 15% I think. You may just be seeing an open space within near the signature. I opened the scanned image in the paint program, and there was a checkbox to reduce size proportionally (I think under the menu item stretch and skew.) You can also crop the image here. Then save as something like "signature2 and import that. I think this will solve the problem.
