I will try to be a bit more clear. an example of someone successfully using a custom background and button card is here:
https://community.home-assistant.io/t/dashboard-with-dynamically-background/353837/24?u=stain3565
this is nearly what i need. i just need to adapt the code that defines “background:” to reflect my test for the text “jpg” and build the url. i have used jinja for templates before and realise this code in the linked discussion is a different language. if it is js, then i guess i am simply not understanding the code i need. I have since tried an “.includes(“jpg”)” line but still not working.
i do understand that “value template” is not what this code is, I was just trying to use an equivalent template logic term to show it was not the editor yaml that was the issue for me but was the logic within the dynamic background definition.