Has to have some history. Has to have a good amount of fan base. Could be just a studio thing of a anime that has some sort of link to another one (i.e Kanon, Air, Clannad by Key)... so guys any anime?
Studio Ghibli has released many timeless anime classics, such as My Neighbor Totoro, The Cat Returns, Porco Rosso, Grave of the Fireflies, Kiki's Delivery Service, and many many more.
Ghibli and it's anime has a lot of interesting characters and history. I would suggest looking into them. I promise you'll have a large fanbase and a lot of material to work with.