For citation purposes consistency is key. Find an example you can live with and follow it, but generally the rule of thumb in citing:
“Whenever a public domain work is used, the author(s) (if known) should be cited. Citation may be made in accordance with any relevant scientific, scholarly, disciplinary or community practice. Additionally, if a public domain work has been curated or made available by a person other than the author, that provider should also be appropriately credited.”
What do you need to cite? All CC attributions should have the same basic information:
* Title of image
* Creator name
* Source of the image (usually in the form of a URL to image source page)
* Any copyright information included with image (such as a watermark)
* CC license information (including link back to CC documentation page if possible)
In the shortest caption allowed by the above, you would put:
caption: Title [hyperlinked to source] (c)Creator, License information [hyperlinked]