You all might be annoyed by this problem of Windows 8. No matter how much you try to change the lockscreen photo or whichever photo you choose for lockscreen but default lockscreen photo remains. Its a cool feature of Windows 8 that lets you add a personal touch to your computer. and its the first thing which appears after booting your windows 8 and you might get sick of seeing the same lockscreen photo again and again. I have also encountered such error and after searching a lot, I found a solution for it. The solution is very easy. Here it goes:
NOTE: Make sure that you are logged in as administrator before proceeding to the steps below and Make sure that your Windows is activated.
STEP 1: Press the Windows logo + [R] keys on your keyboard to launch the Run window.
STEP 2: In the Open field, type gpedit.msc and then press Enter.
STEP 3: When the Local Group Policy Editor window appears, double-click on Computer Configuration, then on Administrative Templates, then on Control Panel, and lastly on Personalization.
STEP 4: Double-click on the Prevent changing lock screen image option.
STEP 5: Select Disabled, then click OK.
STEP 6: Now, double-click on the Force specific default lock screen image option.
STEP 7: Select Disabled, then click OK.
STEP 8: Your lock screen picture problem of your computer should be resolved now.