This image is free to use, both online and offline, as long as you follow the license requirements: you must provide credit to the author (the "attribution" requirement) and you have to distribute the image and anything you make with it under the same free license (the "copyleft" or "share alike" requirement).
You can choose any of the listed licenses, which all grant similar rights and have similar requirements. For simplicity and compatibility, the Creative Commons Attribution-Share Alike 3.0 license is probably the best choice.
Example credit line for online use:
Photo by <a
href="http://ragesoss.com">Sage Ross</a>, <a
href="https://creativecommons.org/licenses/by-sa/3.0/deed.en">CC by-sa<a>
It is also good practice to link the image itself back to the source page here on Wikimedia Commons, so that viewers will be able to get the original if they wish to use it themselves.
Example credit line for print use:
Photo by Sage Ross (ragesoss.com), from Wikimedia Commons. Creative Commons Attribution-Share Alike 3.0 Unported.
It is also good practice to note the file name of the image, so that readers will be able to easily find the original online if they wish.
I, the copyright holder of this work, hereby publish it under the following licenses:
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License.http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue
to share – to copy, distribute and transmit the work
to remix – to adapt the work
Under the following conditions:
attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.