ToString does not necessarily do what you think it does: in many, many cases (and Images are one of those) it returns the name of the class: "System.Drawing.Bitmap" for example.
If you want to store images into a database, you have to convert them to an array of bytes first:
MemoryStream ms = new MemoryStream();
myImage.Save(ms,System.Drawing.Imaging.ImageFormat.Bmp);
return ms.ToArray();
BTW: It is a very, very silly idea to use the
object
class as a property - it removes any chance of strong typing and thus errors being caught at compile time instead of run time. It you want an Image, use the Image class, not Object. Otherwise you also have to cast it to an Image every time you want to use it...