Are you planing on using the titles that go with each snowman because if so I would not make the S.M. to large. With the words and S.M. in the same block it will be rather crowded.
I am thinking also that keeping the S.M. the same size as they are would be a great boarder but may pull your eye away from the main part of the quilt.
These are my ideas, I am sure you will come up with the perfect solution. Good luck!
I too have collected all of them but not yet started any projects yet.