There are two properties specific to Picture Box objects: Image and Image URL (both in the Data section). These are very similar in that you can choose an image to display but the difference is that the image specified in Image is saved in the report while that in Image URL is simply referenced by path. Setting one blanks the other.

If you want to display an image stored in a field in the database, use data binding instead: bind to Image if the field contains the image or ImageURL if the field contains the path to the image.