Here are a few inexpensive quick ideas to use while your scrapbooking. For a kid-themed page press your child's fingers into an ink pad and create a border from stamped fingerprints.
Go through your paper scraps and make some borders with the paper scraps you have.
Mount stickers on metal rim tags and use on your page.
Rubber-stamp words or letters repeatedly across the paper to drive home a theme.
Use a panoramic photo you have as a border for your page.