Picture content control prints blue if left blank

[SlowJoe]

I am using Word 2007 to create a fill-in form. It has some basic things to enter using legacy controls (text boxes and check boxes). I want to allow the user to add a signature if desired using a jpg or bmp. I was able to add a picture content control which seems to work OK. I'm not real comfortable with the fact that the picture can change sizes and be stretched but can live with it. The main problem I am having is if no bmp/jpg is selected, the form prints with a big blue rectangle where the signature should be. Please help. Thank you