waitImages.js

export const waitImage = ref =>
  new Promise((resolve, reject) => {
    ref.onload = (event) => { resolve(event); ref.onload = null };
    ref.onerror = (event) => { reject(event); ref.onerror = null };
  });

const createImage = str => Object.assign(document.createElement('img'), { src: str });
const waitImages = arrStr => Promise.all(arrStr.map(str => waitImage(createImage(str))));

const images = Array.from({ length: 10 }, (_, index) => `https://source.unsplash.com/random?v=${index}`)

export default {
  data: () => ({ isLoading: true }),
  async mounted() {
    await waitImages(images)
    this.isLoading = false;
  }
}

waitImages.vue

<template>
 <img v-for="img in imgs" :src="img.src" :key="img.id" ref="images"/> 
</template>

<script>
const waitImage = ref =>
  new Promise((resolve, reject) => {
    ref.onload = (event) => { resolve(event); ref.onload = null };
    ref.onerror = (event) => { reject(event); ref.onerror = null };
  });

const waitImages = arrImgs => Promise.all(arrImgs.map(waitImage));

export default {
  props: {
    imgs: Array,
  },
  data: () => ({ isLoading: true }),
  async mounted() {
    await waitImages(this.$refs.images)
    this.isLoading = false;
  }
}
</script>