"Ekam sat vipra bahudha vadanti" says the Rig Veda. "That which exists is One: sages call it by various names." This photo, taken in Varanasi, reminded me of that.
Banaras is Shiva's city, he is everywhere you look. At the souvenir stalls, Shiva is represented in colourful popular art as Gangadhara, bearing the Ganges in his hair. But the stalls also sell pictures of a host of other deities - Kuber the God of Wealth, Hanuman, Rama, Krishna, Durga, Kali, Ganesh, Lakshmi ... there are pictures also of objects such as the Sri Yantra, and there are pictures of godmen and gurus - Sai Baba, Ravidas, and many others.
Why are there so many deities, gurus, and other pictures? Because Hinduism allows its practitioners to choose whichever form of God that inspires and resonates with them the most. This is the concept of "Ishta Devata" or "Chosen Deity". Here the form itself is not as important as the ultimate goal. While all Hindus agree there is only one Eternal Brahman, or Cosmic Truth, they reach this Brahman through different routes. That route is the Ishta Devata.
It is difficult to meditate upon an abstract concept. So teachers of meditation tell their pupils to select an Ishta Devata in order to do "Saguna Dhyana" - in this type of meditation the practitioner focuses on the visible aspects of the Ishta Devata. For example, Saguna Dhyana of Vishnu could include meditating one by one on his face, his golden ornaments, his yellow robes etc. You can see this form of meditation being practised by many Bhaktimarga followers.
For Ramakrishna Paramahamsa, the Goddess Kali was his Ishta Devata. He saw her everywhere and meditated solely upon her. Such meditation - usually also done with a specific mantra chanting (involving the name or the characteristics of the Ishta Devata) - can have powerful effects on the mind.
From this type of Saguna Dhyana, the practitioner can eventually move to "Nirguna Dhyana", meditation on the abstract. The Ishta Devata provides a sort of gateway, almost. Obviously, it is important to choose an Ishta Devata that resonates most with you. Many families use the concept of kula-devata or family deity as their Ishta Devata. Many people use the face of their spiritual guru as their ishta-devata. There are really no rules or restrictions. Sincerity is important.
The term Ishta Devata should also be understood as a way to define a chosen ideal or goal. For example, in the Yogasutra, Patanjali says: "svadhyayad ishta devata sanprayogah" meaning that self-study and reflection brings you into contact with the desired ideal.