It appears to be mixed content issue for the reasons Russ said.
The images that do not appear in Linz's screenshot are absolute references using http not https where as the ones that do appear are relative.
As they use different protocols some browsers do not like the mixed content.
It is very easy to replicate the issue in IE on desktop by disallowing Display Mixed Content in security settings. This is a global setting however.
As you said you use IE on your phone it could be the same thing but I'm not familiar with IE on phones and what settings it does/does not have.
In IE on the desktop, the console will log errors such as
SEC7111: HTTPS security is compromised by
http://fordforums.com.au/images/DM3.jpg
File: showthread.php
SEC7111: HTTPS security is compromised by
http://www.fordforums.com.au/images/.../community.jpg
File: showthread.php
SEC7111: HTTPS security is compromised by
http://www.fordforums.com.au/images/medals/tech1.jpg
File: showthread.php
SEC7111: HTTPS security is compromised by
http://www.fordforums.com.au/images/medals/valued.jpg
Chrome - but it does not block it on my computer as they are warnings but the https will change from green lock to grey 'i' icon.
Mixed Content: The page at 'https://fordforums.com.au/showthread.php?p=5897987#post5897987' was loaded over HTTPS, but requested an insecure image 'http://fordforums.com.au/images/DM3.jpg'. This content should also be served over HTTPS.
VM388 showthread.php?p=5897987:4262 Mixed Content: The page at 'https://fordforums.com.au/showthread.php?p=5897987#post5897987' was loaded over HTTPS, but requested an insecure image 'http://www.fordforums.com.au/images/medals/community.jpg'. This content should also be served over HTTPS.
VM388 showthread.php?p=5897987:4262 Mixed Content: The page at 'https://fordforums.com.au/showthread.php?p=5897987#post5897987' was loaded over HTTPS, but requested an insecure image 'http://www.fordforums.com.au/images/medals/tech1.jpg'. This content should also be served over HTTPS.
VM388 showthread.php?p=5897987:4262 Mixed Content: The page at 'https://fordforums.com.au/showthread.php?p=5897987#post5897987' was loaded over HTTPS, but requested an insecure image 'http://www.fordforums.com.au/images/medals/valued.jpg'. This content should also be served over HTTPS.
Some browsers may have an icon in the address bar that when clicked on allow you to show the block content and get around the issue.
The screenshot in cat007's post is weird. It is rendering the images but also looks to be doing the same with the alt text although it is not visible.