Hi Julie, I never bought the autogynephilia theory because it wasn't scientifically backed and I love that GretchenM is providing interesting information about it (interesting because at least her explanation makes some sense, compared to the many ludicrous analysis I stumbled on so far on the Net).
As for being aroused by looking at your own pictures, I think what GretchenM says too (in the first section of her post), it can be explained by the bringing back of memories of an experience that may have turned you on at the time.
Also, my personal opinion, I find it difficult to believe that you can be sexually attracted to yourself, our brains have been wired to be looking for mates since (ok, a little after) dinos walked the Earth, habits so long in the making are hard to give up, and the inescapable proof of this is that a biped can't tickle himself as you probably know. I suspect that members attracted to themselves in car rear view mirrors or other types of reflective or capturing devices are reacting to the female cues their image is sending, and your imagination does the rest to build this feminine creature or concept that sends butterflies to your belly.