I will add, though, if my quilt is not super-precious or I am giving it to charity, I will often just use a pretty sheet from the thrift store as my back. Instant backing, no piecing, and usually less than $5. Yippee!
2. Scrappy rainbow quilt - back (top left). Use a single strip of fun colors to widen a single chunk of yardage enough to fit.
3. Wildlife Portraits WIP back (by Flaun!). Use thin strips of a dark or light solid to frame, outline, or offset chunks of fabric.
4. Kill that Cancer Finished Quilt Back. Inspirational words.
5. blue and black granny square back. Make a giant version of a square from the front.
6. Anne's Quilt - Back. Applique handprints or other meaningful things onto the back of a gift quilt.
7. Rückseite Farbrausch. Consider slicing and inserting a solid into a print.
8. Central Texas Wildfires Donation Quilt Back. A great way to use lots of tiny scraps for big impact. Most of the back is still three giant chunks, which is very fast.
9. Empire Quilt Back. Use one or a few simple blocks paired with giant chunks.
10. geometric quilt - back. Even more small pieces with giant chunks. Love this idea!
11. Back of Finished Confetti Quilt. Just go crazy in your tiny scraps!
12. Mod Mosaic Back-Totally Finished!. Things don't need to be cut straight.
13. Off Centered Sherbet Squares Back. Just small pieces of improvisation have a great impact without being busy or very time-consuming.
Hope that gives you some more ideas!