playing photo slideshow on TV

Are any of the Sansa players capable of being used to playback photos on a tv or monitor? 

No.

There’s a third-party (or maybe homebrew) video-out cable for the Sansa View, but I don’t know if it does photos too.

The View should be able to do this. There’s even a A/V cable with the Sansa coupler on one end and RCA plugs on the other to plug into your AUX IN jacks on your TV.

Can’t say for sure, but I would assume you could view photos, in or out of slideshow format as well as video.