Now, Windows 7 build 7057 has leaked (x86 only). This build is newer (March 5) than any I'd previously seen or used, so I will try to grab it today. JCXP has few details but does offer up the new wallpaper and user picture downloads.
Build 7057 includes quite a few noticeable changes. First and foremost is the new pre/post-desktop screen as shown above. Also in this build are once again some new wallpapers, and some new user account pictures to boot. However, only the default wallpapers have been replaced this time around, the global walls remain the same. As always, these bits are available to download at the links below for you to enjoy!
A few other changes should be mentioned as well. We noted that in build 7048 that the UAC security flaw had yet to be fixed. Well we are happy to announce that this has been fixed in 7057 and users are now prompted with a UAC warning when attempting to change the UAC prompt level. Other small changes include the ability to now resize pictures based on pixels rather than percentages in Paint, as well as being able to maintain the image aspect ratio when doing so. Media Center has also been tricked out with a new anthem-like intro tune and interface sound effects. And good news for you Canadian TV watchers; TV functions no longer cause Media Center to crash when setting your region to Canada.
More info as it comes in.
Thanks to Sebastian V. for the link.