Clear the thumbnail cache by using Disk Cleanup; just press Windows + R, type cleanmgr, select your system drive, and check the box for Thumbnails. Next, check the file associations by right-clicking an affected image, choosing Open with, and selecting your preferred photo viewer, making sure to set it as the default. You can also reset folder options by going to File Explorer, clicking on View, then Options, and selecting Reset Folders under the View tab. Make sure your Windows 11 is up to date by going to Settings > Windows Update. After making these changes, restart your computer. If the problem still exists, run a system file check by opening an admin command prompt and typing sfc /scannow to repair any corrupted files.