Some ways to achieve that
* a high loft batting
* minimal quilting on your snowman, with more on the background
* an extra layer of batting in the snowman.
You can take a look at this snowman that I did last year ...
http://www.quiltingboard.com/picture...t-t209528.html
Not sure if you can notice it ... For the snowbank at the bottom, I added an extra layer of batting to help give it a more puffy look. Then tried to emulate a drift effect with the quilting. Technically right or wrong, it's how I did it!
