Green Thumbnails Picture Previews

So yesterday when I was looking around at my wallpapers from the explorer I noticed that some thumbnail previews for my pictures are green.

I had to cut around the personal pictures. It's not like every picture that's like this. I think these were the ones that I downloaded from the internet or or really low quality pixelated pictures.

And then when I opened my personalization app (?) it started acting funny too. When I choose a wallpaper it never shows a preview it's just stuck with previous wallpaper preview. Even with slideshows this happens. Then I checked the lock screen if it had the same problem. It was worse. At first it did preview but it really takes a while then after a while it was just gray:


Then I noticed this happened to the icons which only now works if I choose windows spotlight



They look fine from the start menu so I really don't know what's happening.

I'm not really sure when this started happening but I noticed this after I installed a theme that I downloaded from my microsoft.com. But I did install an for video thumbnails that doesn't have any by default.
So I don't know, should I try to reset the icon and thumbnail cache? Maybe that got screwed up? I tried to reset the thumbnails by using the diskcleanup tool. I've tried troubleshooting and doing the sfc /scannow none of them are detecting anything. I don't know what to do. Halp.

Things you might try:
from an elevated (admin) command prompt (just as a routine check)
chkdsk C: /F

Create a new user- do you see the same problems? If not, your user profile is corrupt.

An in-place upgrade repair install.
Repair Install Windows 10 with an In-place Upgrade - Windows 10 Forums
This lets you keep everything, windows updates from the major build are redone, you need a boot medium of the same major build you have now.

Ok, so the next option is an in-place repair install.

An In-place upgrade repair install will fix many things, but not those where the settings are not changed by the procedure.

For this you need an installation medium with the same base build as you have installed.
Repair Install Windows 10 with an In-place Upgrade - Windows 10 Forums
This will refresh Windows, after the manner of a Windows installation.
- all/most associations will be unchanged
- all your programs will be left installed
- you will lose any custom fonts
- you will lose any customised system icons
- you may need to re-establish your Wi-Fi connection
- you will need to redo Windows updates subsequent to the build you have used for the repair install
- Windows.old will be created
- system restore will be turned off- you should turn it on again and I recommend you manually schedule a daily restore point.
- you will need to redo any language downloads including the display language if you changed that)

This is one of the better features of Win10: as each major build comes out, that's your updated reference build, and as updates are mostly cumulative, there will be few to do.

Recommendation:
Before you perform this major repair procedure, do create a disk image.

Please consider using disk imaging regularly. It's a brilliant way to
- preserve your system (and your sanity)
- back up your data
- restore your system to a previously working state in a relatively short time

Recommended: Macrium Reflect or Aomei Backupper (free) + their boot disk/device + large enough external storage medium.

Excellent.. the repair technique is one of the good features of Win 10, although it won't fix everything of course.