My theory about quilting is that if it has a lot of straight lines, then use some kind of curvy design or something that illustrates the theme of the quilt. What about upsizing some of these coloring book designs?
https://www.bing.com/images/search?q...book&FORM=IGRE
You could make the quilting as 1 huge design of the favorite character. Office Depot will print the picture on up to 24x36 paper (better check this out for sure) and you can pin that paper to your quilt and sew through it. Use a small stitch and/or dampen your paper after sewing to help rip the paper off. You can do some swirlies or sun's rays or what ever you want on out to the edge of the quilt after you have done the main pattern. You don't have to do every line in the drawing in your quilting, just enough so that you can tell what it is.
Edited to add: If your quilt is much longer than the size I suggested Office depot or Staples could print, then you can split the design on 2 pages and pin them to your quilt. You will need to stabilize your top, batting and backing well. In this instance, I would probably use some type of spray glue. Then pin the pattern very well, starting your quilting sewing from the middle out.