yeah, I've been burned a few times by photos. Luckily, never in a case where the sender couldn't try again using something else (it's only happened on non textsecure to textsecure, if both people use it, I haven't had any issues)
There was a bug a while back where photos would only download via cellular, but the app would try to use WiFi if you were connected. I think it is fixed now.
