State_filter for picture-entity not updating?

Trying to grok state_filters for picture-entity.

Wanting to be able to display some indication that a still image from a camera has not updated in over a minute.

The cameras are remote and sometimes the link goes down temporarily. So it would be great to be able to tell at a glance that the image is stale: Different colored 'name" text, or “Idle” changing to “Stale” or anything else.

Any ideas?

Thanks!

FYI: These are Generic Camera Integrations