cool idea!
i’ve been having issues with card_mod performance and reliability (paying a lot more attention to their documentation now) so this looks interesting
Simple way to add a quick visual recognition is to use emojis - no css or new card needed. Simply copy and paste.
Now that your using button card you can do it easily adding something like:
<ha-icon icon="mdi:water-percent" style="width:3vw;height:3vw;"></ha-icon>
in a [[[ return … ]]]