<div class="row">
  <div class="small-12 columns">
  <h1>Browse users tattoos</h1>
  </div>
</div>
<div class="row">
  <div class="small-12 columns">
    <ul >
      <% @users.each do |user| %>
        <li><h3><%= user.user_name %></h3></li>
          <ul class="clearing-thumbs" data-clearing>
            <% user.tattoos.each do |tat| %>
              <li><a href=<%= tat.image %>>
                <img data-caption=<%= tat.name %> 
                src=<%= tat.image(:thumb) %> 
                class="th radius"></a>
              </li>
            <% end %>  
          </ul>
      <% end %>
    </ul>
  </div>
</div>

<div class="row">
  <div class="small-12 columns">
  <h1>Browse users tattoos</h1>
  </div>
</div>
<div class="row">
  <div class="small-12 columns">
    <ul >
      <% @users.each do |user| %>
        <li><h3><%= user.user_name %></h3></li>
          <ul class="small-block-grid-2 medium-block-grid-3 large-block-grid-4">
            <ul class="clearing-thumbs" data-clearing>
              <% user.tattoos.each do |tat| %>
                <li><a href=<%= tat.image %>>
                  <img data-caption=<%= tat.name %> 
                  src=<%= tat.image(:thumb) %> 
                  class="th radius"></a>
                </li>
              <% end %>  
            </ul>
          </ul>
      <% end %>
    </ul>
  </div>
</div>

Add block grid of varying sizes for better layout.
Add block grid of varying sizes for better layout.
