While users await the release of next build of Windows 10 for Phone, more screenshots of the build 10072 have emerged online. The latest leaks shows-off changes in the Calling user interface as well as for the first time shows-off the Office Excel app to be precise the Excel Preview app.
Calling UI changes
Outlook Contacts app (still in Alpha)
Office Excel Preview app
Build 10072 (10.0.12555.74)