This is how we do it:
<form>
<select name='u_skin' class='forminput' onchange="window.location='/?act=UserCP&CODE=07&u_language=en&u_skin='+this.value">
<?
$DB->query("SELECT uid, sid, sname FROM ib_beta_skins WHERE hidden <> 1");
if ( $DB->get_num_rows() )
{
while ( $s = $DB->fetch_row() )
{
$skin_select .= $s['sid'] == $ibforums->member['skin'] ? "<option value='{$s['sid']}' selected>{$s['sname']}</option>" : "<option value='{$s['sid']}'>{$s['sname']}</option>";
}
$skin_select .= "</select>";
}
print("$skin_select");
?>
</form>
You'd just need to find the right place to stick that code, to get the selector to appear where you want it.