Thanks a lot James. All of your advice is great.
I understand the system a bit more and I think I should generate the file array at application start and place it in some global application store. It’s ‘static’ enough that It shouldn’t have to be refreshed until the application restarts again.
That way, it’s just a list available via user preferences. The custom field is then turned into a URL to display the image everywhere.
Armed with the Ember docs link you provided, I should be able to figure the rest out myself. Thanks again and all the best!