X0lera

const list_pictures = [
  {
    img: 'img',
    counter: 0
  },
  {
    img: ''img,
    counter: 20000
  },
  {
    img: 'img',
    counter: 30000
  },
  {
    img: 'img',
    counter: 10000
  }
]

list_pictures.map( item => {
  setTimeout(() => 
    document.body.style.backgroundImage = `url(${item.img})`
  ,item.counter)
})