Mmm, personally I wouldn't store images within a database, even though it can do it (field defined as a BLO😎. Better to upload the images to a directory where PHP can see/access.
For the form, though, make sure you do have 'enctype="multipart/form-data"' within the <form> tag, or else you will have problems. Also, use the PHP function "move_uploaded_file()" to move the uploaded file/image to the designated directory/folder.