Is the husband's request to his wife—whom he has not yet consummated the marriage with—to expose her body and exchange photos online considered a religious or educational error, and will this affect their relationship in the future and lead her to unwanted sexual thoughts?

If a legal marriage contract has been concluded for you with the girl, then she has become your wife, and it is permissible for you to enjoy her. There is no harm in her revealing some of her body to you or in you seeing her picture. However, caution should be exercised when using a camera over the internet, as someone who is not permitted to see it might view it. This action does not necessarily have negative consequences, so be keen to complete your marriage and consummate it with your wife as soon as possible, and treat her well and raise her according to religion and faith.