Another teacher who's taken part in this challenge - Tara Benwell - has included useful language to express contrast and make comaparisons. It is really useful, so here's a link to her post in case you want to check it out.
I'm including two sets of photos; you can write about either one or both of them, as you like it :), and feel free to comment on any aspect of the pics that comes to your mind, including people, setting, time, details, gestures... whatever.
Set 1
Set 2
Go ahead and start comparing, but... mind your tongue, guys: that bloke showing up in all the pictures is still your teacher :)