What makes a good YouTube thumbnail? My opinions.
I just looked through a list of thumbnails on YouTube and I think I know now what kind of thumbnails I prefer at least:
There should preferably be two people on the thumbnail, facing each other
If there is only one person, there must be text, and the text must not be continuous
An example with continuous text:
A whiteboard or similar can work instead of discrete texts, and it is good if the video title is visible in the thumbnail
A single person with no text I do not think works that well:
And finally a group of people without any text fragments also does not work that well:
So for my tastes, put two people facing each other, or one person with discrete texts or a whiteboard or other teaching instrument!