One more time, with feeling.
I keep a photo collection. I'm the primary visitor. None of you view it, I have the stats to prove it. But it's ok. It's my favorite part of the site.
Even if you aren't going to through the trouble of setting up a site and show all this stuff to the world, you should still take pictures.
Primarily, it improves my memory tremendously when it comes to next year. I remember the lesson and I remember the pictures I took during the lesson and what the intended output was.
If you get to be the kind of person who leads staff development, having a library of classroom photos is immensely helpful. I think at least on four occasions during meetings I've been able to reference one of my kooky ideas by showing the photo that went along with it.
You'll thank yourself at the end of the year when it's time to submit evidence for an appraisal.