Using a graphics editing program, you can digitally scrapbook your photos using the products at Designer Digitals. Save the finished page as a flattened .jpg file. Upload it to Shutterfly the same way you would normally upload a photo.
When you are creating the book, choose the page layout that has a full-page photo and place the scrapbook page in that spot instead of a photo.
If you need help getting started with your project, we have several resources to help:
Getting Started with Digital Scrapbooking