• A thumbnail is a small image representation of a larger image, usually intended to make it easier and faster to look at or manage a group of larger images. Graphic designers and photographers typically use this term.
• What i can give you for an high quality eye catching thumbnail:-
1. Include title text to deliver context.
2. Use the best font style.
3. Fine contrast with bright background.
4. Use a relevant and great image.
5. Include an image of the face: Make eye contact with the viewer.
6. Analyze your competitor.
7. Create a design for a small screen.
8. Optimize for different devices.
9. Using Better colour combination to attract your Viewers.
10. Export at high quality.