My idols suitable for worships
Can be any one of eight types.
It may be a sculpture made in wood
Or made with flower and sandalwood.
It may be one that made of diamond
Or one that is built with mere sand.
It can also be pictures or paintings
Or in one’s heart as mental pictures.

Those who pray to me for power
May offer anything such as flower.
Those devotees who don’t desire
Anything at all in return but Me
Can do the offerings in their minds.

Let those who worship me in their hearts
Offer all the nice flowers etc; to me
By their very own mental creations.

(Maha Bhagavatham
Ekadasa Skantham- Chapter-27.)