Some creators will explicitly state how your attribution to their work should look. Here is an example from The Noun Project:
And here is an example from FilmMusic.io:
If the creator does not give specific direction on how to attribute their work, it is best to include, at a minimum, the Title, Creator, Source, and the original License.
Title: The name given to the work by its creator. Not all works are given an explicit title by their creator.
Creator: The person or persons who made the work. User names are also acceptable.
Source: Where the work is available. Sources might include Instagram, Twitter, DeviantArt, etc. Anywhere creators have hosted their works.
License: The terms given in order to use this work. This might be the Creative Commons License, or other specific terms given by the creator.
It is considered a best practice, when you are able, to link back to the creator's profile and/or link back to the original content. If the content is under a Creative Common's License, linking to the license is also ideal. An example from Creative Commons is available.
Just like when citing in MLA or APA, not all information will always be available with all works. Give as much as you can. As with all citations, the goal is for the original work to be discoverable.
"Island in the Sun" by Lisa Zins is licensed under CC BY 2.0
Title and Source - The title is given, and links to the original image posted on Flickr
Creator - Name is given and links to their user profile on Flickr
License - The type of license is listed and links to more information about the license on the Creative Commons website
Creative Commons Best Practices Wiki