Using close-up facial expressions—especially those conveying high-energy emotions—to build a direct biological connection with the viewer. Curiosity Gaps:
Ideally, a thumbnail should contain no more than three main elements (e.g., a face, a subject, and a short text block) to avoid visual clutter. The Rule of Thirds: thumbnailexpert
A thumbnail expert is often the "decision-maker" for whether a video succeeds or fails before it even starts. Thai YouTube Thumbnail Expert Needed - Facebook thumbnailexpert