A helper function for Omeka to retrieve any number of random featured items. Include this function in your Omeka theme's custom.php file, and use wherever you'd like to get some random featur

Custom Random Featured Items helper.php

<?php
/**
 * Custom function to retrieve any number of random featured items.
 *
 * @param int $num The number of random featured items to return
 * @param boolean $withImage Whether to return items with derivative images. True by default.
 * @return array An array of Omeka Item objects.
 */
function custom_get_random_featured_items($num = '10', $withImage = true)
{
    // Get the database.
    $db = get_db();

    // Get the Item table.
    $table = $db->getTable('Item');

    // Build the select query.
    $select = $table->getSelect();
    $select->from(array(), 'RAND() as rand');
    $select->where('i.featured = 1');
    $select->order('rand DESC');
    $select->limit($num);    

    // If we only want items with derivative image files, join the File table.
    if ($withImage) {
        $select->joinLeft(array('f'=>"$db->File"), 'f.item_id = i.id', array());
        $select->where('f.has_derivative_image = 1');
    }

    // Fetch some items with our select.
    $items = $table->fetchObjects($select);

    return $items;
}