Here Lord Shiva sits crossed legged. This pose is called Padmasana or lotus seat.
The Stalk of the Lotus is held by two Naga (Snakes).
The Headgear of Lord Shiva is elaborate and his head is surrounded by usual nimbus. The expression on his face is calm and contemplative.
The arms and legs of the sculpture are severely damaged but the position in which Lord Shiva is sitting can be any of the pose shown below in the illustration
We can recognize this sculpture as a representation of Lakulisa (a.k.a. Lakulisha, Nakulisha), which according to the puranas, was the 28th incarnation of Lord Shiva.
It is said that Lakulisa was born in Kayavarohan, Varodara District, Gujarat. He is also said the founder of Pashupata Shaivism Sect. It had huge emphasis on Yoga system.
You can read more about Pashupata Shaivism here. Link.
Flying above the central figure are celestial guards.
On the extreme right of the sculpture we could see Lord Bramha sitting on his vehicle of swans and …
…Lord Vishnu sitting on his Elephant (Airavat).
Under the left knee of Lord Shiva appears to be a Sunflower.
Lord Vishnu riding Garuda. Both the faces are destroyed.
There is a draped female attendant on both sides of the central figure.
These female attendants hold a fly-whisk.
According to various sources, this sculpture on the lower part seems to be of the Sun God.