If you’ve been using the same Kodi configuration for quite some time now, then experiencing issues with Kodi thumbnails displaying incorrectly isn’t uncommon. Luckily it’s something that can be fixed very easily.
In this case, thumbnails refers to any icons or posters that are used by Kodi addons. This method will allow you to reset the Kodi textures database in order to fix the issue, without losing any content at all.
Step 1: Navigate to the File manager under the SYSTEM menu.
Step 2: Click on the Profile directory item on the left side of the window.
Step 3: Select the Database folder.
Step 4: Highlight the Textures.db file.
Step 5: Open the Context menu and then click on the Delete function.
Step 6: Press the Yes button to confirm.
Step 7: Return to the Kodi home screen at this point.
Step 8: Click on the Power icon at the bottom left of your screen.
Press 9: Press the Exit button and you’re done!
Once you’ve rebooted your Kodi setup, the thumbnails should work perfectly again.