I agree with Jake Archibald here that an image’s alt text should try to evoke the same emotions as its visuals so screen reader users don’t miss out.
Let the creative writing begin!
The relevant parts of an image aren't limited to the cold hard facts. Images can make you feel a particular way, and that's something that should be made available to a screen reader user.
It isn't just a head-shot of me. I'm doing a thing. I'm peering from behind a plant and pulling a bit of a silly face. There's humour expressed in the image. I'm not saying that it's going to win any comedy awards, but the image expresses a particular tone, and that matters. So, it should go in the alt: “Head-shot of me, a pale white guy, wearing glasses, grinning slightly, and partially hiding behind a plant”.
Source: Writing great alt text: Emotion matters by Jake Archibald