We're getting a few isolated reports, ourselves included, that some Live Tiles are not updating their images properly or just general strangeness with notifications. While this was common on NoDo with Mango it's been very rare, if ever, that we've had failures occurring.
The most popular culprit seems to be the official Foursquare app, which for many now features a blank tile instead of your local rankings. In addition, we've see our GoVoice app stuck on "1" and even our own WPCentral app not have the back-tile update. Dave Amenta (interview), developer of Send to WP7, confirmed with us that he too is experiencing these problems.
For now, all we can think of is some hiccups with Microsoft's push notification servers, which handle a lot of this back end stuff. We'll keep an eye out and give a shout out in comments if you're Tiles are not refreshing or other craziness.
Image credit: puredrive07, from our forums