It should be a negligible effect on the database. It’s not like the image gets dumped directly into the SQL database – it just gets uploaded to a folder.
I’m not even totally sure there’s a discrete reference to the image in the database, outside of the public URL freetexted into whatever comment it’s in. Because once it’s there, I can’t delete the image as a user. (Maybe the admins can delete it via some database reference though?)