Artificial Intelligence Generated Content (AIGC) is increasingly positioned as a transformative influence in creative disciplines, yet its pedagogical functions in design education remain conceptually underexamined. This paper presents a conceptual analysis of AIGC integration in environmental design education, advancing a theoretically grounded framework informed by constructivist learning theory, design cognition, and spatial cognition research. Rather than framing AIGC as a technological innovation alone, the study reconceptualises it as a form of cognitive and representational support that mediates ideation, visualization, and reflective design processes. Through conceptual synthesis of interdisciplinary literature, three propositions are developed: (1) AIGC may facilitate spatial reasoning and creative exploration by expanding external visual representations; (2) its educational value is contingent upon pedagogical mediation, including instructional design, guided critique, and reflective engagement; and (3) cultural and disciplinary knowledge function as interpretive constraints shaping the appropriation and transformation of AI-generated outputs. The paper contributes a structured conceptual model clarifying how AIGC may influence learning processes, offering theoretical directions for curriculum design and future empirical inquiry in design education.