This website encourages remixing so your picture must be licensed under a Creative Commons license. Ideally you should have a primary copy of the picture in Wikimedia Commons or similar.
Be sure to check and erase metadata you do not want attached to the picture. Especially watch for GPS location and other metadata that you do not want public. This website is stored in an open respository and it may be impossible to remove the information from the Internet even if removed from the repository.