Learn English – Proper way to cite Wikipedia according to the Chicago Manual of Style

The first thing you need to nail down is which "Chicago Style" you are supposed to be following. The Chicago Manual of Style, 15th Edition (2003) offers this observation (under the heading "Legal Citations," at 17.275):

Stylebooks. Citations in predominantly legal works may follow one of three guides: The Bluebook: A Uniform System of Citation, 17th edition, published by the Harvard Law Review Association in 2000; (2) the newest style guide, the ALWD Citation Manual: A Professional System of Citation, prepared and published by the Association of Legal Writing Directors and Darby Dickerson in 2000; or (3) The University of Chicago Manual of Legal Citation, 2d edition (2000),edited by the staff of the University of Chicago Law Review... Whichever system you choose, follow it consistently throughout a work.

So if you want to follow "Chicago Style" and your work is "predominantly legal," you should consult the University of Chicago Manual of Legal Citation, not the Chicago Manual of Style, for guidance. I direct your attention, in particular, to Rule 4.2(A)(c)(2) of that style guide:

Supreme Court reporters. Supreme Court cases should be cited in the following order of priority:

1st — US reporter cite if it exists.

2d — S Ct reporter cite if it exists.

3d — WL cite if it exists.

4th — LEXIS cite if it exists.

Unfortunately, as far as I can tell, the UCMLC doesn't discuss how to cite a syllabus to a Supreme Court decision; but in Rule 4.3(c) it suggests that supplementary content associated with a particular court decision may be identified in roman before the name of the case. Consequently, I would consider the following format analogous to the one it approves for "citation to online copy":

Syllabus to Maroonbook v Blue Book, 666 US 999 (2014).

where "666" is the volume number in U.S. Reports (the preferred collection of Supreme Court decisions) and "999" is the page number where the syllabus appears.

On the other hand, if your work is not primarily legal, you're back at square one, trying to figure out the relevant Chicago Manual of Style style—and that book isn't especially helpful for handling legal citations. Still, at 16.106 of the 15th Edition, CMoS provides some basis for adopting the following bibliographical style:

U.S. Supreme Court. 2014. Maroonbook v Blue Book, syllabus, 666 U.S. 999.

The allied note form, closely modeled on CMoS 17.284, would be much the same as the bibliographical form except for the shifting of the year to a parenthetical at the end of the citation, and the omission of the institutional author:

1. Maroonbook v Blue Book, syllabus, 666 U.S. 999 (2014).

where "1" is simply the number of the note in the relevant chapter or article.

Whatever style you adopt, you won't be able to point to a rule in Chicago that specifically endorses it, but I think that the styles I've suggested are in line with Chicago's preferences in related areas and should keep you out of trouble. For additional advice, I recommend consulting the most recent Harvard Blue Book (which I don't have) to see if it addresses your particular citation situation.

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.