A thumbnail is an invitation
A small preview helps someone choose a project to explore. It cannot show the complete rhythm of a website. Give the project a page of its own so the typography, imagery and sequence can be seen at a useful size.
Show the whole composition
A long page capture reveals how a design develops from the opening to the footer. Readers can compare the large moments with the quieter sections between them. Keep an uncropped version available so the work can be explored beyond the first screen.
Put a little context around the image
Name the brand, describe the type of website and explain the focus of the design using information that can be verified. A useful case study does not need invented results or a long list of technologies. Clear context and the actual work are enough to begin the conversation.
Be clear about older work
A live website can change after a project is delivered, and some websites eventually close. Keep an archive image when it helps document the original design. Label the difference between an older portfolio image and a current website capture so the presentation remains honest.