Shiva, Is Yogeshwar, the yogi par excellence. The Lotus has always symbolised purity, beauty, a blossoming of the soul,and therefore it symbolises enlightenment in most spiritual and mystic traditions

Lord Shiva seated on a lotus? that is a rare depiction indeed! Shiva, Is Yogeshwar, the yogi par excellence. 
The Lotus has always symbolised purity, beauty, a blossoming of the soul,and therefore it symbolises enlightenment in most spiritual and mystic traditions
But here , in this beautiful picture, a second lotus is also being shown. At the crown of Shiva, is The sahasrara chakra . Sahasrara means the thousand petalled (lotus) therefore denoting infinity. Shiva's true nature is the timeless infinite, and through dhyana, meditation, yogis can enter into the gateway and have a glimpse of their beloved Lord's Nature.
So Shiva , who is rarely shown seated on a lotus, seems to project the chakra system in this picture.
Sahasrara signifies that consciousness is anant ananda-
It is its own endless bliss. Lord Shiva started many systems of Yoga and Tantra. Devotees like Gorakh Nath and many other adept yogis transmitted them for the benefit of their followers.Therefore the original Hatha Yoga also comes from Shiva, He is the Adi Yogi.
Aum Namah Shivaya!