Problem

Some images are not displaying on a Confluence page.  You might see an endless spinning or loading image instead.  

There is nothing present in the logs.

Cause

While there can be other causes for this, one known cause is Adblock Plus.  

Adblock will sometimes block images:

• with common ad dimensions in the file name, e.g. 'myimage_720_90.png' or 'myimage_300x250.jpg'.
• with common ad keywords in their path (and file name), e.g. banners, adv, ad.
• maybe other filters that analyse CSS or HTML
  
  

Workaround

• Disable AdBlock Plus 
• Check and possibly rename the files, check the entire URI for strings that will trigger Adblock.