The Shadow monsters in the MoTP include dusk beasts (two headed shadow lizards) and umbral banyans (big carnivorous trees). The Fiend Folio, if you have access to it, has a lot of creatures, including shadow fey, the dark ones from 1e (also in the Tome of Horrors), and various shadow asps and darkweavers. Undead, especially shadows, wraiths and nightshades, are a must.
Demiurge out.