From the New and Improved TOS, everything you upload "belongs" to them:

With regard to any file or content you upload to the public portions of our site, you grant Imgur a non-exclusive, royalty- free, perpetual, irrevocable worldwide license (with sublicense and assignment rights) to use, to display online and in any present or future media, to create derivative works of, to allow downloads of, and/or distribute any such file or content. To the extent that you delete a such file or content from the public portions of our site, the license you grant to Imgur pursuant to the preceding sentence will automatically terminate, but will not be revoked with respect to any file or content Imgur has already copied and sublicensed or designated for sublicense. Also, of course, anything you post to a public portion of our site may be used by the public pursuant to the following paragraph even after you delete it.

From the New TOS, everything you upload "belongs" to them:

With regard to any file or content you upload to the public portions of our site, you grant Imgur a non-exclusive, royalty- free, perpetual, irrevocable worldwide license (with sublicense and assignment rights) to use, to display online and in any present or future media, to create derivative works of, to allow downloads of, and/or distribute any such file or content. To the extent that you delete a such file or content from the public portions of our site, the license you grant to Imgur pursuant to the preceding sentence will automatically terminate, but will not be revoked with respect to any file or content Imgur has already copied and sublicensed or designated for sublicense. Also, of course, anything you post to a public portion of our site may be used by the public pursuant to the following paragraph even after you delete it.