The image depicts what we call "Rubin's vase or Rubin face or figure-ground vase". When two fields have a common border, and one is seen as figure and the other as ground.(from wikipedia Rubin_vase)
This is a completely free image Rubin's vase that you can download, post, and use for any purpose.
Image License: CC0 No Rights Reserved
You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission, and at no cost. This image is completely free.