Tool to sniff a network and show the pictures which get transmitted

I am preparing for a little presentation on Wifi security / dangers of public networks to a non technical audience and wanted to do a demonstration to make things a little more visual. My idea is to use a tool I had years ago which would look for network packets containing image data and would compile them as they get transmitted. And with this tool active I would ask someone in the audience to navigate to a non https website and then see the images on my PC/projector. It's a small crowd of elderly people, so the risk of catching something inappropriate should be small. :-)

But, I can't remember what the tool was called and my search attempts didn't reveal anything. Anyone got an idea?

Or maybe an idea for an even better demo?