Steps:

/maspawn sign.large
/sil <my image url>
everything looks good
restart server
signs are present
images are not there - blank sign entity

I posted the signs at the Outpost if that helps.  Thank you

Did you check to see if the sign image data is in the profile's data file? I think people have seen a few times that it doesn't save for some reason. Once you confirm that it saves in the data file, it should work after restarts/reloads.

I've been able to reproduce the issue by spawning a sign with the plugin, and then running o.reload MonumentAddons. After that point, running sil* on signs isn't detected because the plugin isn't subscribed to the Sign Artist hooks. The dynamic hook subscriptions were implemented as a standard performance optimization, since there's no need to listen to Sign Artist events if Monument Addons hasn't spawned any signs yet. However, there is a bug, where as the plugin is reloading, the old plugin instance is still despawning signs, and then tells the new plugin instance that a sign has despawned, which is offsetting the number of signs the new plugin instance thinks are present. I will release a fix in the next update.

Until the fix is released, you can simply run o.unload MonumentAddons, wait a few seconds, run o.load MonumentAddons, then using Sign Artist commands should be detected.

I cannot find anything related to SignArtistImages or URLs in the data file   :(