Module.register("MMM-Rediscover",{
                default: {loc: 'modules/MMM-Rediscover/images'},
		count : 0,
		files:[],
		start : function(){
				var self = this
				self.sendSocketNotification("GET_FILES",self.config.loc)
				setInterval(function() {self.updateDom()}, 3000);
		},
		getDom : function (){
                        var wrapper = document.createElement('div')
			wrapper.id = 'GPHOTO'
			var img = document.createElement('div')
			var i = this.count
                        img.style.backgroundImage = 'url(' + this.files[i] + ')'
			img.id = 'photo'
        		var blr = document.createElement('div')
			blr.id = 'backgrnd'
			blr.style.backgroundImage = 'url(' + this.files[i] + ')'
			wrapper.appendChild(blr)
			wrapper.appendChild(img)
			len = this.files.length
			this.count = (this.count == len-1) ? 0 : this.count+1
                        return wrapper
                },
		getStyles : function (){
			return ['MMM-Rediscover.css']
		},
		socketNotificationReceived : function(notification , payload){
			if(notification == "OBTAINED"){
				this.files = payload
			}
		}
})

My node_helper file:

var NodeHelper = require("node_helper")
var file = require("fs")
const spawn = require("child_process").spawn
module.exports = NodeHelper.create({
		start : function(){
			var process = spawn("python", ["modules/MMM-Rediscover/images/Photos.py"])
			process.stdout.on("data", (data)=>{console.log(data)})
		},
		socketNotificationReceived: function(notification, payload){
			if(notification == "GET_FILES"){
				var payload = this.getFiles(payload)
				this.sendSocketNotification("OBTAINED",payload)
			}
		},
		getFiles : function(loc){
			const contents = file.readdirSync(loc)
			ret = []
			for ( var i = 0; i < contents.length; i++){
				extension = contents[i].split('.').pop().toLowerCase()
				if (extension == 'jpg'){
					var currentItem = loc + '/' + contents[i]
					ret.push(currentItem)
				}
			}
			return ret
		}
})