Speaking of new features and tweaks, Facebook is testing a small Instagram icon in the bottom-right-hand corner of mobile news feed photos uploaded via the photo-sharing application that actually brings users out of Facebook and into Instagram.

Sister blog Inside Facebook discovered the icon, saying that tapping it from the Facebook iPhone app brings users to the Instagram app and automatically loads their photo streams, while doing so from the Facebook mobile site opens a new browser window that displays the photo on Instagram’s mobile site.

Inside Facebook believes (and we agree) that the test is likely part of Facebook’s efforts to boost discovery and installations for apps that integrate its open graph.

Readers: Have you seen this Instagram icon, or similar icons for other apps?

Screen grab courtesy of Inside Facebook.