did this for the school last year! I posted 3 different levels of pictures (easy to hard) and had a writing section underneath to guess. Students who guessed closest or the right one got a brag tag I made. See my I wonder board for pictures I have used.
This is a great resource for teachers who are unfamiliar with inquiry- based learning to use. It breaks down each step of the inquiry process for the teachers, and different ways to use it in the classroom.