SovBundle/Resources/assets/app/adminlte/field/filemanager/form.scss

.lc-filemenager-preview {
  width: 100%;
  object-fit: contain;
  position: relative;
  min-height: 80px;
}

.lc-filemenager-preview .no-image{
  position: absolute;
  font-size: 3rem;
  width: 100%;
  height: 100%;
  z-index: 1;
  top: 0;
  text-align: center;
  left: 0;
  right: 0;
  margin: auto;
}
.lc-filemenager-preview img{
  width: 100%;
  z-index: 2;
  position: relative;
  object-fit: contain;
}