First find the background you like most and paste the code below that background to the "About Me" section of your profile.
Now you can leave the background as it is or you can ALSO copy and paste the code below to make the boxes on your layout transparent so the background shows better. I highly recommend this!
Or if you want to get rid of those boxes entirely, then use this code:
4th of July
Christmas
Easter
Father's Day
Flag Day
Halloween
Memorial Day
Mother's Day
New Year
St. Patrick's Day
Thanksgiving
Valentine
Baby
Birthday
Graduation
Wedding