Back to school idea - "We're looking back on summer, this is what we see!" Have students draw pictures of things they have done over summer break in sunglasses. You could also do it for things students are looking forward to this year.
Next open house, I'm doing this! Back to School Photo Booth Props - Since kids don't know each other at all yet, it might be nice if on the first day, they come in to the classroom greeted by pictures of themselves taken at Meet the Teacher Night!