On the Northern Wall of the Sree Thyagarajaswamy temple, Thiruvottiyur.
This is the Ekapada Murthy aspect of the Trimurtis.
There can be many interpretations. The one given by the heritage tour leader, Pradeep Chakravarthy was this:
It was a time when Jainism and Buddhism were kept at bay by Hinduism. However, there was friction between various factions of Hinduism. This depiction of an integrated form of Shiva, Vishnu and Brahma was to highlight the fact that all philosophies converge.
This is also sometimes referred to as Tripaada Trimurthy since a leg each of Brahma and Vishnu are also seen.
Another interpretation is that this showcases the supremacy of Shiva as the axis of the world or its cosmic pillar