Quora’s answer to What is Quora’s Policy on Sex-Related Content? What is Quora’s policy about nudity and sexual images? What about answers and comments that use sexual language/content in questions that aren’t about sex?
Sexual and sexually-provocative images. Sexual, sex-related, and sexually-provocative images are only allowed on pages involving adult topics and which have been tagged with the appropriate Quora Adult topic(s) (i.e., Specific Types of Adult Content, Sex and/or other topics), which will restrict its distribution. See How can I control whether I see adult content on Quora?
Because user profile pictures appear throughout the site, sex-related image content are not permitted in profile pictures.