Random map generator, hohoho. Random factions would require cards, eh?
As for the art, which is my business then, I think I could come up with something in these lines:
This is an example of seals used in Final Fantasy XII. Each one is from a summoned monster called esper, and it should resemble them physically. The art in the cards could be similar, with less details, cleaner, but all with the same sort of visual identity. Not a banner.