Ganesha is the lord of intelligence, represents the best of both Shiva and Parvathi. He has the light of Shiva and the power of Parvathi. Hence, worshipping Ganesha Painting is the same as worshipping Shiva and Parvathi. He has the qualities of both and embodies in himself the existence of both. Thereby, he represents creation itself, which is described in the scriptures as the union between Purusha (Shiva) and Prakriti (Parvathi). Hence, by worshiping him we earn the merit of worshipping both Shiva and Parvathi.
To see the original painting visit here: https://dirums.com/artwork-details/ganesha-2691