How to make a YouTube thumbnail that gets clicks
Keep one clear focal point, such as a face or a single object, and let it fill the frame. Use at most four words of large, high-contrast text so it stays readable at the small size shown in search and suggested videos.
Test your design at mobile size before publishing. If you can’t tell what the video is about in a second, simplify. Use bold colors that stand out against YouTube’s white and dark interfaces, and keep the style consistent across your channel so viewers recognize you.