A reference board is more useful when it answers a specific design question. Collecting popular thumbnails without notes can encourage imitation while providing little insight into why a layout is clear.
Choose a narrow question
Study one topic, such as showing a small object, placing text on a photograph, or comparing two states. Select examples relevant to that problem rather than mixing every attractive image into one board.
Annotate the observation
Write what each example demonstrates and what remains uncertain. You can observe that a subject occupies most of the frame; you cannot infer from the image alone that this caused the video's view count.
Turn the lesson into a brief
Summarize the useful principle and apply it with appropriate assets for your own video. Keep source links attached to the references. Before production, remove any example that encourages a promise or visual treatment inconsistent with your footage. The board should guide decisions, not become a template for copying.