Here is a standart field.tpl.php file wich we can find using path: root/modules/field/theme.
{syntaxhighlighter brush: css;fontsize: 100; first-line: 1; }<div class="<?php print $classes; ?> clearfix"<?php print $attributes; ?>> <?php if (!$label_hidden): ?> <div class="field-label"<?php print $title_attributes; ?>><?php print $label ?>: </div> <?php endif; ?> <div class="field-items"<?php print $content_attributes; ?>> <?php foreach ($items as $delta => $item): ?> <div class="field-item <?php print $delta % 2 ? 'odd' : 'even'; ?>"<?php print $item_attributes[$delta]; ?>><?php print render($item); ?></div> <?php endforeach; ?> </div> </div>{/syntaxhighlighter}Inside foreach loop we insert just one line before any other and we get what we need.
{syntaxhighlighter brush: css;fontsize: 100; first-line: 1; } <?php $item['#path']['options'] += array('attributes' => array('rel' => $element['#field_name'])); ?>{/syntaxhighlighter}
If we add rel attribute in order to implement fancybox gallerry we should note that all images with the same rel attribute wil have navigation between each other inside gallery window.