I think I had some softwares do a cleaning job and they are definitely not that compatible with the latest developer preview... In the following snapshot there should be 5~6 default pictures to choose as lock screen, however as you can see now they are gone... Any ideas how to resolve this? By the way, the pictures themselves (C:\Windows\Web\Screen\) still exist. They just don't show up here in the Metro Control Panel... Very weird.
Sadly nobody knows the answer... I don't really know what happens, as the only thing I used is CCleaner.
you could do a refresh.(click on control panel,then general,there will see refresh)i had a problem with the metro ui and it fixed that.need to have your disc ready as it may ask for it.if your computer is set to boot from disc,if refresh requires a restart with the disc still in drive,if you see message to push any key to boot from disc,dont do anything and refresh starts.(far as i can remember thats the way it worked.(sorry if thats kind of vague but did it a while ago)if it keeps restarting booting from disc after repair,remove the disc,as i think mine rebooted again so i took it out)hope that helps.
The only way you can get them back is to reinstall 8102 after using cleaning software. Ccleaner is ok to use, but after I used Boostspeed, even system restore wouldn't get them back.