Someone would have to be actively scanning the frequency of your cell before you started sending it, intercepted the packets sent along to transmit the pic, and then you'd have to do all that through a computer with a program that would interpret the data and put it into image form.
Of course, you'd also need a scanner that could actually data scan at the high frequency of the phone (they're not like they used to be, you need very special scanners to even scan that high for most carriers) AND you'd have to be able to break their datastream encryption.
So basically, for it to be unsafe, you'd have to have a cracker (bad version of a hacker, not a white guy
) with the exact right equipment, the right programs, and the right know-how to use everything in conjunction- ready and waiting at the exact moment that you hit send on the photo, and within range of your cellphone's transmission.
Most pics take a matter of only a few seconds, maybe up to 30, to upload.
People with that kind of technological and cracking firepower are not in it to randomly spy on your uploaded bits and pieces.
Bottom line is, it is pretty much impossible- for all intents and purposes- for someone snatch a picture you transmit.
Hopefully that helps alleviate some fears.