Any variable to print no permissions in the showthread??

[kh99]

What does the custom link link to? Is it a vbulletin page? If so then you might be able to check in that page by writing a plugin. If you're linking directly to an image then I think all you can do is replace the link with something else, like

<vb:if condition="!is_member_of($bbuserinfo, A, B, C)">
// custom image link code
<vb:else />
// a link to a "no permission" page
</vb:if>