Even as Windows Insiders play with the recently-released build 10049 of the Windows 10 Technical Preview, leaked screenshots and a change log for a more recent build, 10051, have made their way to the Internet.
The screenshots and change log come from frequent Windows 10 leaker "WZor". As you might expect, the 10051 build doesn't have much in the way of visual differences, although the Start menu does show icons for the upcoming Mail and Calendar apps.
The change notes show that Windows 10 will now use a file dialog box for apps, instead of the file picker that's currently available for Windows 8.1 apps. It's not likely that Microsoft will release this build to the public as part of the Technical Preview as they usually wait to add major new features before launching builds.