Hi Chris,
How to post a clickable image is included in the PhotoRadar FAQ page which is linked to in the sticky, here's a direct link to that particular point:
http://www.photoradar.com/photoradar-faq#forum - this will also show you how to get the correct URL from an image in our gallery as right clicking on that won't get you the right one.
However I wasn't aware that so many of our users were interested in using tags, so I'll make this a sticky for people who want to via that route.
Best wishes,
Amy