Use fontawesome icon as background image

index.slim

form
  .form-group
    .image-upload
      label for="society_image" class="input-lg"
        span
          | Upload Society Picture
      = f.file_field :image, placeholder: "Upload Society Picture",class: 'form-control input-lg inputfile'

style.sass

.image-upload
  positon: relative
  input
    display: none
  label
    cursor: pointer
    background: #fff
    border: 1px solid  $input-border
    width: 100%
    color: $input-color-placeholder
  &:after
    content: '\f0ee'
    font-family: FontAwesome
    font-style: normal
    font-weight: normal
    position: absolute
    color: #ddd
    font-size: 30px
    right: 15px
    top: 3px