Sri Sri Ravi Shankar
Linga is the identity, something with which you know. Infinity is something that cannot be seen with finite senses. So an effort to make infinity seen in the finite or identifying divinity which is infinite is what Linga is all about.
The genitals are also called Linga and when a baby is born only through the genitals does one know if its a boy or a girl. Similarly an object with which you can see that which is beyond the object, that which is summum bonum of the creation is called Linga. Sahasra Linga indicates the vast diversity in the creation. Everything indicates you to the unmanifest, glory of divinity. And to say that the shilpis or sculptors put many many lingas in one, to say that infinity has infinite identities, infinite ways to know it does exist.
Divinity has no form no boundaries but to identify the divinity you need some reference. So all the murtis or vigrahas are made. Statues are not divinity. Statues point you towards the divinity and so for people who are gross, who cannot comprehend the vastness, huge statues are made. But yogis they always move to the subtle, from the gross. Your mind needs to be refined. So they do not keep big statues at all. No yogi has ever established a big statue. If you see all the 12 Jyotirlingas, they are all very small. Agama shastras also say that the murti should be shorter than the size of the person. Very few ancient temples have very big statues, which were mostly established by kings. Kings mean big ego. People with big ego feel satisfied when there is a big statue. People who are humble don’t need to see big statues.
Actually Shiva Lingas are not supposed to have faces at all but we start putting faces on Shiva Linga. Shastras even forbid you to worship Shiva as a form, except Nataraja that too in some places.
Shiva Linga was kept in 3 parts, Brahma, Vishnu and Mahesha. Two parts are invisible and one part is visible to the eyes to say that Shiva is not just what is visible but what is not seen to the eyes is twice of what can be seen. Meaning to indicate that you close your eyes and know the Shiva Tattva from within. Get into meditation, know Shiva and move from gross to subtle. In this journey from gross to subtle, mantras are better than Shaligram and silence is better than mantras.