Can't change lock screen on windows 8.1

Even I am suffering from the same problem!!!

the problem is exactly the same,,,when I click on any of the lock screen it keeps on loading and the selected screen never appears as preview. even no notification apps can be added to the lock screen.the same problem exists when I try to change account picture..getting frustrated..suggest a sollution

Yes I have clicked on the browse button and I have tried every picture in my pictures folder but I still get the same blank screen.

Try putting other pictures in your pictures folder that you do not have.  Something in the formatting may be an issue.  Try making copies of a few of the pictures and give the copies differing names than what they currently have, and try to select the copies of the pictures with the new names and see if that changes anything.  I had to do that with two of my pictures before they would show up again in the lock screen.  I do not know why.

Sorry I forgot to get back to you from this post. I tried copying and renaming a picture like you said and that worked. Thanks for the help!

You are welcome.  Glad it worked for you.  Hopefully, it will be as it is with me and you will never see that issue again.

Go to the following Directory :

C:\ProgramData\Microsoft\Windows\

Now Right click on the folder named "Systemdata"

Left Click "Properties"

Left click on the "Security" tab

Left click on the Advanced" button located around the bottom right corner

where it says "Owner" at the top on the second line of text click the option to "Change" which is a blue text color.

when the new window pops up Left click the "advanced" button

when the new window pops up left click "Find Now"

out of every thing the list finds and pulls up to view at the bottom of that window scroll all the way down and you should see you're user name and email address. Left click on it and then left click on ok.

Click ok again on this older window thats still up.

now left click on "SYSTEM" under the "Principle" tab section

Now left click on the "Edit" button

under the "Basic Permissions" list check the "Full Control" option

left click "ok" (window will close)

left click apply and then "ok" (window will close)

left click apply and then "ok" (window will close)

You and anyone else should now be able to change your lock screen photo with no stuck loading screen.

This is a coding flaw on Microsoft's part by not allowing the system to access the file directory and read/write/modify certain files. I went through very hard lengths to learn how exactly to fix this issue as it had really got on my nerves that I spend almost $130 on windows 8.1 and then yet another $100 on the Windows 8.1 Pro Pack and after installing and completely updating running into this devilish little coding error from Microsoft that wouldn't allow me to change my lock screen photo. I thought "welp...better search and help others fix this since it gave me so much trouble to figure out on my own". 

My personal opinion is Microsoft should have caught this before releasing 8.1 or at least fixed it in a update and my other opinion is that after a Microsoft tech had the audacity to try and offer me $100/30 days of software support even though the flaw is obviously in 8.1 and not any of the users faults (including not mine like the tech was trying to force on to me) that I should be thanked for fixing their problem and reporting it publicly like this so they can get it fixed for their customers. I love Microsoft I think they are a very innovative company so don't take anything in this post the wrong way I am simply giving constructive criticism and trying to help others users as well as the Microsoft team.

Yes I have clicked on the browse button and I have tried every picture in my pictures folder but I still get the same blank screen.

Try putting other pictures in your pictures folder that you do not have.  Something in the formatting may be an issue.  Try making copies of a few of the pictures and give the copies differing names than what they currently have, and try to select the copies of the pictures with the new names and see if that changes anything.  I had to do that with two of my pictures before they would show up again in the lock screen.  I do not know why.

Sorry I forgot to get back to you from this post. I tried copying and renaming a picture like you said and that worked. Thanks for the help!

I did not catch it writing to the registry when I made changes to the pictures.  I did see it use the UI.xaml property to do something, though.  I'll have to look deeper but I think it did something in my AppData folder.  I just need to see if I can find anything.