The best practice would be to list the Creator’s name, the title of the work, link, and any edits you have made.
Suppose you wanted to use the image below on your website.
A good attribution might read:
"Pile of Coins from Different Countries" by Philip Page. Licensed under CC-BY 4.0.
That is a little wordy so feel free to adjust it to your site's needs.
Shorter example: image via Philip Page.