Abstract: Illustrated letterforms occupy a complex space between writing and image, combining graphemic structures with pictorial strategies that surpass conventional typographic classification. Rather than using typological or stylistic approaches, this article conceptualizes illustrated letterforms as graphemic constructions, in which the structural identity of the letter is determined by visual and pictorial operations. A taxonomy is proposed based on the specific operations by which letters are constructed. This study explores how illustrators and designers combine image and letterform into unified visual units, analyzing methods that preserve legibility while introducing visual, narrative, or symbolic elements. It covers diverse contexts—from manuscript traditions to modern graphic practices—focusing on operations that merge image and graphemic structure. Existing classification systems, especially in manuscript studies, often focus on narrative, iconographic, or stylistic criteria. This article emphasizes construction by operation, examining how graphemic structures are actively shaped by pictorial strategies. By shifting attention from style or function to operation, the framework offers a systematic way to describe and compare illustrated letterforms across media and over time. The taxonomy highlights varying degrees of integration between graphemic structure and pictorial elements, from decoration to full integration. This approach positions illustrated letterforms as a distinct area within visual-graphemic creation, emphasizing design, interpretation, and visual problem-solving rather than treating them as marginal or anomalous.