Step 1: Concept Identification: The query concerns the primary subject matter of K.C.S. Paniker, a foundational figure in South Indian modern art and the originator of the Cholamandal Artists' Village.
Step 2: In-depth Analysis: K.C.S. Paniker was instrumental in the Madras Art Movement. In his later, most recognized period, he transitioned from representational art to a distinctive abstract style. This style, termed "Metaphysical landscapes" or part of his "Words and Symbols" series, drew heavily from indigenous Indian traditions. His artworks featured script-like marks, algebraic formulas, astrological diagrams, and conventional symbols. Consequently, his work is best defined by the application of diagrams and pictograms. He devised a visual vocabulary that was both abstract and contemporary, yet firmly grounded in Indian mystical and folk heritage. Although his earlier pieces may have contained figures or themes, his lasting legacy in modern art lies in his symbolic and calligraphic abstraction.
Step 3: Conclusive Determination: The most distinctive element in K.C.S. Paniker's later paintings is his incorporation of diagrams and pictograms.