This is a shop button for the 'SlickPro Graphite' theme. Again, like most modern themes, it doesn't use individual images for the buttons (this theme's buttons are actually quite simple).
Code modifications:Open Themes/SlickPro_Graphite/index.template.phpFind:
if ($context['current_action'] == 'theme')
$current_action = isset($_REQUEST['sa']) && $_REQUEST['sa'] == 'pick' ? 'profile' : 'admin';
Add after:
// Shop
if ($context['current_action'] == 'shop')
$current_action = 'shop';
Also, find:
// The [calendar]!
if ($context['allow_calendar'])
echo '
<td class="main-navigation"><a href="', $scripturl, '?action=calendar">' , $txt['calendar24'] , '</a></td>';
Add after:
// The shop
echo '
<td class="main-navigation"><a href="', $scripturl, '?action=shop">Shop</a></td>';
Then, your shop button should be working