Firefox Screenshots helps you quickly take and easily share screenshots. Images are shared through a web-based URL, and a number of people visiting those links don't use Firefox, which means the Screenshots site might offer an opportunity to convince non-Fx users to try the world's greatest browser.
I was tasked with coming up with some experiment options we will also A/B test. I played around with notification bars, in-page content blocks, footer links, and interstitials. The experiments will be running soon, so check out Firefox Screenshots and let me know if any Firefox promotion UI shows up for you!