Problems with Sharepoint Click Thumbnail Displays?

Good Day Techyv Friends!
Have you experienced problems with the Sharepoint click thumbnail display?
I am experiencing problems with my Sharepoint 2012 in which the thumbnails are not displaying.
Can anyone please tell me what seems to be the problem and help me so that I can see the display in thumbnails?
If you can, please guide me how to create thumbnail gallery in Sharepoint.
Thanks in advance.
