What is the ruling on selling stickers or pins that have the cover image of a foreign book containing some violations?

Selling foreign books is not prohibited merely because they are foreign. Rather, the consideration is their content. If the books are free from Shariah prohibitions, then it is permissible to sell them; otherwise, it is not. This ruling also applies to Arabic books.

Similarly, selling pictorial posters for books follows the ruling of the book itself. If the book's content is permissible, then it is permissible to sell its posters. But if the book contains Shariah prohibitions, such as advocating for disbelief or indecencies, then it is not permissible to sell anything that promotes it, because that would be aiding in sin. Allah has forbidden cooperation in sin and aggression, as He Almighty said: "And do not cooperate in sin and aggression."