Playdough is a great ice-breaker/settling activity for the first day of school.
You could have some playdough for each of the kids to take home, but first they could create and draw their own playdough creation.
These templates include a variety of wordings:
It's going to be a won-doh-ful year
Doh not be shy! Open me up and make something!
We're going to have DOUGH much fun this year!
Also comes in black/white versions.
For more back to school ideas, check out these free guides: