I'm participating in a portrait challenge and wanted to create a crowd for this image... So, I made a seamless brush of a crowd in Procreate and then applied to the final image. It's fun to have instant crowds!  Pictured are: the line art of the portrait, the actual "tile" of the brush and the final project. Thank you Nic for the info!  I may use it to create other busy brushes (leaves? clouds? confetti?)