I will often double batt a wallhanging. Usually I use a combo of W&N and wool or 80/20 and wool. Have also substituted poly for the wool. Doubling gives definition to the quilting and unquilted areas look like trapunto. Here are samples of wallhangings I did this treatment to:
Dragonflies and Iris quilted by feline fanatic
Tealfalcon's Pumpkin Pie quilted by Feline Fanatic
These two are double batted plus a trapunto type treatment:
Blue Heron wall hanging
Toni Whitney Blue Heron wallhanging
This one is double wool
Gail's Heron Pond Quilted by Feline Fanatic
And this one is double wool plus trapunto treatment also done with wool
Quan Yin - A show quilt
When I don't double, I prefer to use a heavier batting so it hangs better like W&N, Quilters Dream cotton or 80/20.