i don’t sync photos to my watch, and if I go to the Photos app on my watch is says there are no photos. However if I go to General->About (where it lists how many songs, photos etc are on the watch) is says there are 15 photos on the watch.
I posted a thread about this last November. Can't confirm why this happens, but myself and a couple others on the forum have seen the same issue. In the months that I've owned my S4, I've seen the photos count fluctuate from 15, down to 6, back up to 15. I've chalked it up to it being maybe a software glitch...
I have about 20 photos synced to the Watch when it shows 35. My guess would be some full colored watch faces are being stored as pictures on the Watch. Hard to say which ones exactly though.