Images in Finder or the Desktop not showing preview images.

Ok so with the installation sometimes preference files get corrupted so try this.

Again Click on the Desktop, now click on Go in the menubar and select Go To Folder.

Enter this text ~/Library/Preferences press Go

A new Finder window will open up, now scroll down to com.apple.finder.plist move this file to the Trash but do not empty it just yet (if there are other instances of this file with random numbers and letters after the .plist extension move these to the Trash also).

Restart your Mac, the finder preference file will regenerate, once the Mac has finished booting up go back to Show View Options and make sure that Show icon preview is selected. Has this made a difference, if so you can empty the Trash.

You could also try setting up another user account and see if that will allow you to see the icon preview.

Click on the Desktop, click on View in the menubar and select Show View Options, make sure Show icon preview is checked.