I hit Pinterest for some DIY ice princess costume ideas for both my girls, and I figured I could come up with something for their dolls as well.
This frigidly elegant gown was super easy to make, with no sewing and only three main "ingredients." I used a Disney Princess (Ariel) dress-up skirt and tied it in the shape I wanted with a strip of white tulle. Then I tied another piece of tulle at the neck and embellished it with some decorative snowflake brads I had on hand. I added more snowflakes to her side-swept braid and topped it off with a tiny tiara (from the party section at a dollar store).
My daughters had a few of these princess dress-up sets, and I love using them for their dolls now that they have both outgrown them. The Cinderella skirt would also work well for Elsa, and the Ariel skirt could make a great doll-sized mermaid, fairy, or princess. Try playing around with pieces you already have for great Dolloween fun!