The actual image that has been uploaded here is no. 23 in the collection there. Those wishing to verify origins will need to hunt a bit; the images do not have their own URLs. As for the copyright information, there is a link on the main page ("Derechos:"), or you can click here: https://creativecommons.org/publicdomain/zero/1.0/
The image is one of several from what was apparently a pack of postcards featuring bullfighting scenes, mostly photographs (like this one), but the odd painting as well.
The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.
http://creativecommons.org/publicdomain/zero/1.0/deed.enCC0Creative Commons Zero, Public Domain Dedicationfalsefalse