For a lot of the questions I'm seeing on ELaU, it seems the answer is ultimately arbitrary and unlikely to be resolved by poll. Since style guides exist to settle the question for people who care not what sounds better, but just want to get with the program and follow a uniform convention, what manual of style should I use for technical writing for US Federal Government documents?
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I would say yes, that is the correct way to go. The CMOS does not explicitly ask for licences, but it does not say they should not be there, either; in fact, according to CMOS 16, section 14.274 Audiovisual materials—elements to include,
Documentation of a recording usually includes some or all of the following pieces of information: the name of the composer, writer, performer, or other person primarily responsible for the content; the title, in italics or quotation marks, as applicable (see 8.192); the name of the recording company or publisher; any identifying number of the recording; indication of medium (compact disc, audiocassette, audiovisual file, etc.); and the copyright date or date of production or performance. Recordings consulted online should include a URL or DOI (see 14.5, 14.6). Supplementary information, such as the number of discs in an album and the duration of the recording, as applicable, may also be given. [my emphasis]
The CC licence information is clearly supplementary information in this context, albeit of a different type than the one they mention as an example.
In section 14.280 Online multimedia, they do not really say much that is very useful in the text, but the example citations given do give some hints, particularly the following example which quotes a YouTube video:
“HOROWITZ AT CARNEGIE HALL 2-Chopin Nocturne in Fm Op.55,” YouTube video, 5:53, from a performance televised by CBS on September 22, 1968, posted by “hubanj,” January 9, 2009, http://www.youtube.com/watch?v=cDVBtuWkMS8.
Adapting this for your photo credits, I would personally go with something like one of the following options:
“taxi,” Flickr photo, taken 11 December 2006, posted by Carolina Arevalo, 20 September 2010, https://www.flickr.com/photos/carolinaarevalo/5008340224 (accessed June 16, 2015). Licence at https://creativecommons.org/licenses/by/2.0.
“taxi,” digital image, taken 11 December 2006, posted to Flickr by Carolina Arevalo, 20 September 2010, https://www.flickr.com/photos/carolinaarevalo/5008340224 (accessed June 16, 2015). Licence at https://creativecommons.org/licenses/by/2.0.
(I would leave out your own description of the image in the Photo Credits section—that belongs as a caption to the image or in the body text, not as part of the credits.)
In cases where you do not have the name (or even a user name) of the photographer, but only their Flickr ID, you’ll just have to write that instead of the actual name:
“taxi,” digital image, taken 11 December 2006, posted to Flickr by user “13548987@NO9”, 20 September 2010, https://www.flickr.com/photos/carolinaarevalo/5008340224 (accessed June 16, 2015). Licence at https://creativecommons.org/licenses/by/2.0.
Best Answer
Well, before my question gets closed I better answer it.
U.S. Government Printing Office Style Manual is one of the better known style guides.
More recently there has been a lot of talk about plain language, and this sometimes shows up in legislation. The plain language publications tend to have a lot more about English usage.
There are agency specific guidelines, but I'll let someone more ambitious than me track them down.