This is the best I could come up with using the Lovelace UI Picture Entity Card
- type: vertical-stack
cards:
- type: glance
title: Nest Protect
entities:
- entity: binary_sensor.upstairs_nest_protect_online
name: Online
- entity: sensor.upstairs_nest_protect_battery_health
name: Battery
- entity: sensor.upstairs_nest_protect_color_status
name: Status
- type: horizontal-stack
cards:
- type: picture-entity
entity: sensor.upstairs_nest_protect_smoke_status
name: Smoke
state_image:
"Ok": /local/nest-icons/nest-protect-green.png
"Warning": /local/nest-icons/nest-protect-yellow.png
"Emergency": /local/nest-icons/nest-protect-red.png
- type: picture-entity
entity: sensor.upstairs_nest_protect_co_status
name: CO
state_image:
"Ok": /local/nest-icons/nest-protect-green.png
"Warning": /local/nest-icons/nest-protect-yellow.png
"Emergency": /local/nest-icons/nest-protect-red.png
This card type will change the picture for both CO and Smoke depending on ‘state’