https://github.com/bazzel/ember2-workshop, tag 4.0.0

form.hbs

<div class='form-group'>
  {{#if model.image}}
    <img src={{model.image}}>
    <button type='button' class='remove pull-right'>Remove</button>
  {{else}}
    <img src='http://placehold.it/320x150&text=No image'>
  {{/if}}
  <div class='file'>
    Browse...<input type='file' accept='image/*'>
  </div>
</div>

upload-file.js

import Ember from 'ember';

export default Ember.TextField.extend({
  type: 'file',
  change(e) {
    var reader = new FileReader();

    reader.onload = (e) => {
      var fileToUpload = e.srcElement.result;

      Ember.run(() => {
        this.set('file', fileToUpload);
      });
    };
    return reader.readAsDataURL(e.target.files[0]);
  }
});