Describe the selection
Put the collection's purpose into a short sentence. It may group a product type, introduce a seasonal range or bring together items around an intended use. The sentence should describe this selection closely enough to help decide whether a product belongs.
Compare the proposed items with that purpose. An awkward fit can reveal a useful question about the grouping. Discuss it before trying to make the page look coherent through image treatment alone. The selection and the visual direction should support the same idea.
A collection page has several visual choices to make. Image scale can give a product more space; a crop can draw attention to a detail; typography can explain the grouping before the items begin. Decide which of those choices serves the collection's purpose.
Keep the product information readable and the relationship between neighbouring items deliberate. A strong arrangement can include variation, but the variation should have a reason. It should not make similar items difficult to compare simply because every tile wants to be distinctive.
Connect the homepage presentation
If the collection appears on the homepage, consider what that smaller introduction can communicate. Its image and wording should prepare the reader for the selection they will find after following the link.
Keep a record of the agreed direction and the material it depends on. When the range changes, that record helps the business decide which visual choices still belong. A collection's role should be understandable enough to guide an update, not just a single presentation prepared for the first day it appears.