Is there a way to add an underlay to a predefined item model ?

[dusky oyster]

I would like to have a background applied to some item models when they have certain custom data. Is it possible to do it without having to either :

• redefine all supported item models to include an underlay
• create a single item model which would handle all the model variation at once
  ?

[fossil surge]

Don't believe so, no

[small wyvern]

The only easy way to do that is to change the base item model but that means all items could have that background