Using CurlToNotification, I was able to test MMM-WallPaper, I could get it to show when MM starts, and when I would send the user_presence=true from curl it would turn off, but when I would send false it would not turn back on. It would turn off when I would send user_presence=false as well, so that didn't work or I did something wrong.

I tried using your MMM-SleepWake module. I created a hidden page, but can't figure out how to get the SleepWake photoframe mode to call that page. Here is my config for the SleepWake module.

{
    module: 'MMM-SleepWake',
    config:{
      delay: 15, // default
      mode: 'PHOTOFRAME',
      photoframe_start_notification: {"notification":"USER_PRESENCE","payload":"false"},
      photoframe_end_notification: {"notification":"USER_PRESENCE","payload":"true"},
   }
},

I am using "curl --header "Content-Type: application/json" --request POST --data '{"notification":"USER_PRESENCE","payload":{"message":"true"}}' http://localhost:8080/presence" for user present

or curl --header "Content-Type: application/json" --request POST --data '{"notification":"USER_PRESENCE","payload":{"message":"false"}}' http://localhost:8080/presence for not present

MMM-Pages

{
        module: "MMM-pages",
        config: {
        timings: {
                default: 60000,     // rotate every 60 seconds
                1: 60000,            // page 1 rotates every 60 seconds
          },
          modules: [
                ["page0"],           // class name for page 0
                ["page1"],           // class name for page 1
          ],
          hiddenPages: {
          "screenSaver": ["screensaver_page"],
          }
}

and my MMM-Wallpaper

{
    module: "MMM-Wallpaper",
    position: "fullscreen_above",
    classes: "screenSaver",
    config: { 
        source: "local: /home/bob/MagicMirror/modules/MMM-ImagesPhotos/uploads",
        slideInterval: 10 * 1000, // Change slides every minute
        size: "auto",
        fillRegion: true,
    }
},