i love using the wide batik's regular ones and flannel ones they make awesome beautiful backs. shop around they can be found at much less than $20 a yard. but what you put on the back of your quilt is your personal preferance, use what you like. batiks really up the cost of the quilt (and value) they are beautiful!
i did buy a 3yd batik wide backing one time then hemmed it and use it for a sheet...i just couldn't put it on a quilt. everyonce in a while when i'm making the bed i will think i should put it one the back of a quilt but, it stays a sheet:)