The most important aspect of creating a video is probably the thumbnail with a suitable video title. The thumbnail must grab attention and immediately convey what the video is about without revealing too much information, so that the video retains some suspense. Of course, it must also match the title; more on that in this article (still in progress).

 
The thumbnail should be 1280 × 720 pixels or at least 640 pixels, but a higher resolution is always better so that the image appears sharp and the text is easily readable.

Nevertheless, the text should be printed in a larger font, as the majority of users consume content on their smartphones.

In my opinion, the corresponding channel should be immediately identifiable from the thumbnail, as this is the only way to maintain high brand recognition and significantly increase the likelihood of views and subscriptions.

If you run your channel in multiple languages, it's important that the thumbnail clearly indicates the language of the video. I find it annoying to have to look several times because the title doesn't specify which language the video is in.
I solved this problem by adding flags to each thumbnail to indicate the language. Of course, I didn't just download these flags from somewhere; I created custom icons because I want to appeal to all users in English and German, regardless of whether they're from England, America, or Australia. Therefore, I opted for a flag consisting of half a US flag and half a UK flag. For German speakers, I've created a combined flag design using the Austrian, German, and Swiss flags. I hope this will appeal to a wider audience.

 To immediately identify which tutorial it is, it's helpful to use the program's icon. If it's not a program, you can create your own icon that you can always use for this type of tutorial, or even for video thumbnails.