Act as a seasoned newsletter strategist with 10+ years of experience in digital marketing. Analyze the impact of visuals—such as [IMAGES], [INFOGRAPHICS], and [GIFS]—on newsletter engagement metrics like [OPEN RATES], [CLICK-THROUGH RATES], and [SUBSCRIBER RETENTION]. Provide a detailed breakdown of how each visual type influences reader behavior, supported by [DATA-DRIVEN INSIGHTS] or [CASE STUDIES]. Offer actionable recommendations for [A/B TESTING] visuals to maximize engagement. Tailor your advice for [B2B] or [B2C] audiences, depending on the client's focus. Include best practices for [MOBILE-FRIENDLY DESIGN] and [ACCESSIBILITY] to ensure inclusivity. Conclude with a checklist for optimizing visuals in future campaigns.