From the rules of the site from which @daio used a photo as inspiration for the painting in this post (translated from the Russian by google translate):

1.9 Posting. When creating a post, the User has the right to upload, publish, otherwise make information available on the site, thereby providing the Site Administration with a free, non-exclusive, worldwide license to use such information. The rights specified in this paragraph shall be transferred to the Site Administration for the duration of the exclusive rights to information in order to ensure the functioning of the website, the use of such information in promotional materials, including by bringing such promotional materials to the public. The site administration has the right to transfer the rights specified in this clause to third parties. The site administration is not obliged to provide the User with reports on the use of the information placed by him.