If there's no permission needed, you should license this under a Creative Commons license using the deviation submission form. That way it'll show up on a Google Image search when you search for "free to use or share" (yes, Google can do this).
You can do this without re-uploading the deviation; look right under the download link, hit the Edit button, go down to the bottom of the page, select "Publishing Options", then select "License".
Creative Commons license allows free sharing and usage of the work. Attribution is required. You can select whether or not you want commercial uses of the work to be allowed under license. You can also select whether or not you want derivative works of this image to be allowed under license. You, as the copyright holder, may waive any selected conditions for specific people. More information here.