What comes across before the words?
I want an image to give an initial sense of the world you are entering. Light, a material or a gesture can say more than a general view. A website screenshot shows an interface. It does not always make you want to explore it.
So I look at the image on its own, without a title or a logo. If it needs a long explanation to work, it probably belongs later in the story, alongside the detail it illustrates.
The atmosphere has to belong to the subject.
An attractive photograph can promise the wrong project. I prefer to start with images of the place, its objects or its uses. The connection should be easy to explain.
The question is more than “do I like it?”. Why this image here? What does it add that the next images do not already say? A cover and evidence of the work serve different purposes.
Choose within the actual frame.
I compare candidates in the page: large, small, then on a phone. Cropping can remove the gesture that made the image interesting. A subject near the edge can compete with the title.
A contact sheet makes decisions easier: equal formats keep the subject visible and reveal differences. I keep several candidates until I see them in the composition. The decision belongs with the page, not just a folder of files.