There are many things worshipped in temples that are not devas, but however, have some divine association (like: the holy place (tirtha), snakes (nagas), the mount of the gods (vahana), guards of the temple (dwarpal), etc.). Depending on the sampradaya one is from, they are seen as a manifestation of god himself, or very dear to the lord, hence mandated to be worshipped. In some temples, even devotees of gods are worshipped. Again, it can be interpreted as devotee = god or very dear to god, so we worship.
Hopefully, that answers your question. Forgive me if I made any mistakes or if the writing is poor.