tap/app/views/orders/_user_list.html.erb

<div class="col-md-6">
  <h3 class="center" >sort by name</h3>

  <% users.each do |user| %>
      <div class="thumbnail overview">
        <%= link_to image_tag("http://placekitten.com/g/50/50", class: "img-circle dagschotel"), user %>
        <% if user.avatar.exists? %>
          <%= link_to image_tag(user.avatar), new_user_order_path(user) %>
        <% else %>
          <%= link_to image_tag("http://babeholder.pixoil.com/img/100/100", class: "img-circle user_img"), new_user_order_path(user) %>
        <% end %>

      <%= link_to user.name , new_user_order_path(user), class: "btn btn-info",
        style: get_color_style(user) %>
    </div>
  <% end %>

</div>