new.html.erb

<div class="container">
  <%= form_for @album, url: albums_path, html: {class: "nifty-form"} do |f| %>
    <%= f.label :name %>  
    <%= f.text_field :name %>
    <label for="images" class="custom-file-upload">Upload Images</label>
    <%= f.file_field :images, id: "images", multiple: true, onchange: "myFunction()" %> 
    <%= f.submit "Create" %>
  <% end %>
  <p class="sub-head">Images selected</p>
  <p id="demo"></p>
<script>
function myFunction(){
    var x = document.getElementById("images");
    var txt = "";
    if ('files' in x) {
      if (x.files.length > 0) {
        for (var i = 0; i < x.files.length; i++) {
          txt += "<div class='upload'>" + "Image" + " " + (i+1) + "</div>";
          var file = x.files[i];
          if ('name' in file) {
            txt += "<div class='upload-name'>" + file.name + "</div>";
          }
        }
      }
    }
    document.getElementById("demo").innerHTML = txt;
}
</script>
</div>

new.scss

.container {
    max-width: 600px;
    margin: 0 auto;
}

.nifty-form label {
    font-size: 15px;
    font-family: sans-serif;
}

.nifty-form input[type=text] {
    width: 100%;
    padding: 12px 20px;
    margin: 8px 0;
    display: inline-block;
    border: 1px solid #ccc;
    border-radius: 4px;
    box-sizing: border-box;
    font-size: 16px;
}

.nifty-form input:focus {
    border: 1px solid grey;
}

.nifty-form input[type=submit] {
    width: 100%;
    background-color: blueviolet;
    color: white;
    padding: 14px 20px;
    margin: 8px 0;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 16px;
}

.custom-file-upload {
    background-color: blueviolet;
    color: white;
    padding: 14px 20px;
    margin: 8px 0;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 16px;
    display: inline-block;
}

.nifty-form input[type="file"] {
    display: none;
}

.sub-head {
    font-size: 18px;
    font-family: sans-serif;
}

.upload {
    font-size: 15px;
    font-family: sans-serif;
}

.upload-name {
    font-size: 15px;
    font-family: sans-serif;
    margin: 5px 0px;
}