Windows Explorer - thumbnails for JPG fail if over 10MB

You do have the option to reset Windows 10, although that should be done after all of our options have been eliminated because it removes your programs.

I'm not sure how you cleared your icon cache, but if you didn't already do this, try it:

1. Press Ctrl+Shift+Esc to open Task Manager.
2. Go to Details tab.
3. Kill explorer.exe. Taskbar will disappear. (the time, icons, etc.) Before doing this, make sure you aren't copying any files or anything.
4. File > New Task in Task Manager, type cmd.exe and click OK (check the run with admin box).
5. Type cd %LOCALAPPDATA%\Microsoft\Windows\Explorer into Command Prompt and press Enter.
6. Type del /f /q *.db and press Enter.
7. Type explorer.exe into Command Prompt and press Enter. Taskbar will reappear.
8. You are free to close those windows.

And if that doesn't work, try setting the built-in photos app as the default photo viewer instead of ACDSee. The program associated with the file can affect the thumbnail it displays. To do that, search for "default apps", and scroll down until you see the default photo viewer option. Choose Photos as the default and check to see if the icons begin displaying properly.

Then, use the Command Prompt troubleshooting option.

1. Click Start button.
2. Click Power.
3. Hold Shift and click Restart.
PC restarts.
Blue screen shows up saying "Choose an option"
4. Click Troubleshoot.
5. Click Advanced options.
6. Click Command Prompt.
Screen turns black and PC restarts.
Screen says "Preparing Command Prompt".
Blue screen that says "Command Prompt" appears.
7. Click on any user that is in the list.
8. Type the password for that user. If it doesn't have a password, don't type anything.
9. Click Continue.
10. In Command Prompt, type D: and press Enter.11. Type cd users\your username\appdata\local\microsoft\windows\explorer and press Enter.
12. Type del /f /q *.db and press Enter.13.Close the window.
You are now in the "Choose an option" screen.
14. Click Continue.

If that does not solve the problem, I would advise running the SFC /SCANNOW command in Command Prompt to scan for and fix corrupt system files.
https://support.microsoft.com/en-us/kb/929833