Can you please tell how you are customizing folder? Are you choosing icons from icon files like .ICO, .DLL,.ICL etc...? Also have you checked Folder options where the required options are selected or not?
How to Restore Desktop Icons to Their Default Settings
Right click on your desktop background using the computer mouse.
Select "Personalization" from the menu.
Click "Change desktop icons" under the "Tasks" menu in the top, left-hand side of the Personalization menu.
Click the "Restore Default" button in the "Desktop Icon Settings" window that opened