People act like they've never updated the carrier file before.
An official carrier update notification comes through iTunes when you plug your phone in. Just like when there is a firmware update, you'll get a notification that there is an updated carrier file. Install and this will activate the MMS functionality of the phone, and make the camera icon available to you in SMS so that you can select a picture.
The MMS functionality is already on your phone if you have 3.0 or higher, it's just currently hidden. This carrier file updates the phones settings, and makes this functionality visible.