Shiva is not worshipped in human form (Murthi Puja) Shiva is worshipped in Linga form. The Linga is symbolic representation of Nameless formless infinite and absolute nature of ultimate reality.
The Linga was designed to represent Unity of God, (the upper cyclindrical part) his supremacy over the three Gunas of Prakrthi (the three stripes in lower part of any properly sculpted Linga). -IDEAL TO KEEP IN TEMPLE -VERY AUSPICIOUS TO DO SHIVA POOJA.
The lingam (also, linga, ling, Shiva linga, Shiv ling, Sanskrit लिङ्गं, liṅgaṃ, meaning "mark", "sign", "gender", "phallus", "inference" or "eternal procreative germ") is a representation of the Hindu deity Shiva used for worship in temples.
Whether the lingam symbolizes the physical body of the god or something purely spiritual is the topic of many a century-old debate within Hinduism.
Description
The lingam has been interpreted as a symbol of male creative energy or of the phallus though today most Hindus view the linga as a symbol of divine energy rather than as a sexual symbol. The lingam is often represented with the yoni, a symbol of the goddess or of Shakti, female creative energy. The union of lingam and yoni represents the "indivisible two-in-oneness of male and female, the passive space and active time from which all life originates". The lingam and the yoni have been interpreted as the male and female sexual organs since the end of the 19th century by some scholars, while to practising Hindus they stand for the inseparability of the male and female principles and the totality of creation. The Hindu scripture Shiva Purana describes the worship of the lingam as originating in the loss and recovery of Shiva's phallus, though it also describes the origin of the lingam as the beginning-less and endless pillar (Stambha). The Linga Purana also supports the latter interpretation as a cosmic pillar, symbolizing the infinite nature of Shiva.