I've been running a Mystic Lilies campaign for over a year now, and one of the best choices I made for it was to buy adoptable designs for the NPCs. The campaign has a big focus on the NPCs - they're not just throwaway characters, they're important cast members, and having art for all of them has really helped develop them. Buying adoptable designs made this actually affordable - I really recommend people try this out next time they're running a TTRPG campaign.
(artist info is in the alt text; all the title cards I made for the adopts I got are under the break)