When my daughter turned 2 I had no idea what theme to have for her birthday party.  Her birthday is in February and that year she began singing Frosty the Snowman.  So, I had a snowman party for her.  I cut out snowflakes from paper and hung them from the ceiling.  We made snow men out of white balloons and placed them at each table.  And for party hats I went to a supply store and bought black plastic top hats they had left from New Year's.  It was fun doing something out of the ordinary and everyone loved it. If you're lucky enough to live where there's snow you could build a big snowman to greet your guests too.