My cards don't have dialogue because I am too lazy to bother writing any and nobody proposed to write for them, but I have already done that as a tech demo.
The missing BG is a common bug with my mod, otherwise it's easy to do.
The data structure I am talking about is a CardEntity, they are stored in a Dictionary in StaticDataManager (a Singleton).
If you aren't already, you should use UnityExplorer (included in the mod package), it is really helpful to find out what you are looking for.
If you want, you can read Manager.cs in my mod files. This is the class that interacts with the game engine to inject the custom cards.