So, my current "Adopt a Plugin (TM)" efforts include auto-generating the sidebar for each library and plugin of ImageJ2 core and Fiji. As part of this, we could make it reference the correct external image link.
Regarding the security issues: ideal would be to allow external images only from whitelisted domains. We can research how to do this later. @aneevel, could you please add this to LOCI's sysadmin to-do list?
This would also make it possible to externally reference Zenodo badges for non-core plugins, though they would need to be manually updated with each release (already generally true).