These styles are really format templates which are activated as the form is
created. You have 3 options:
1. Manually change the background. Go to the Design View. Open the property
sheet. On the format tab, change the picture property by going to the
ellipses (...) at the end of the picture property box, clicking on it and
choosing a new picture. Manually change any of the textboxes and label
styles.
2. Create a form and all the items on it that you want as a style and set it
as a Template in Tools ... Options ... Forms/Reports