Problems with form design and themes

Hello

I am having some problems with the form design and themes of the forms. I tried every option and I cant seem to get rid of the background image, I even tried to load a black image but it will not work. See the attached screenshot of my form, you will notice the bacgroud stribbed image and a piece that shows trough the form (marked in a red circle.

Thank you, the code worked to remove that piece of background in the form. But I can't see how to remove the page background picture. Here is the link to the form. It shows above the form.

http://form.jotformpro.com/form/30044900489957