Official comment
Due to the blending function of the slideshow, there is no ability to mix from a photo to a video; the slideshow must first be stopped, but if you already have a video track loaded and playing on one of the decks, it will switch from the slideshow photo to the video almost instantaneously.
There is no "auto repeat," but you could simply loop the entire track manually by pressing the IN button at the beginning of the track, jumping to the end of the track (using your mouse or the needle search) and then press the OUT button.