This issue has been resolved by installing the Windows 8.1 update from Microsoft.
Win 8.1 will now allow me to change my Account or Lock Screen picture. When I attempt to do either, I see the "waiting" animation (little dots circling). Sometimes an error will report that it cannot change the picture.Created another account on my laptop (Inspiron 15 Notebook 3521) to determine if the problem was only associated with my primary (Admin rights) account. Unfortunately the issue exists with this new account, too.Verified the Registry entry at: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Desktop\NameSpace\B4FB3F98-C1EA-428d-A78A-D1F5659CBA93.Thanks for your assistM
Cannot change Account or Lock pictures in Win8.1