Pictures / Apple Watch faces

Is there any way I can toggle between an Apple Watch face and one of my pictures?

i think I may be going mad but when I first got my watch I set it up with one picture and one of the official faces and when I tapped the watch screen it would toggle between the two.

now for some reason it doesn’t, it stays static on only one of them.

am I going mad or was this an actual feature? Is so, how do I get it back?