jQuery datatables image sorting

Sorting with jQuery datables, pretty easy but with images having images and "-" is bit difficult. I manage to do it for string, date and int but for images I can't think of anyway,

What I really want is to sort images and leave row which has value "-" at bottom,

http://jsfiddle.net/CYubV/73/

JS

$.extend($.fn.dataTableExt.oSort, {
    "date-eu-asc": function (a, b) {
        if (a == '-') return 1;
        else if (b == '-') return -1;
        else {
            //return ((a < b) ? -1 : ((a > b) ? 1 : 0));
            // what going to go here ?
        }
    },

        "date-eu-desc": function (a, b) {
        if (a == '-') return 1;
        else if (b == '-') return -1;
        else {
            //return ((a < b) ? 1 : ((a > b) ? -1 : 0));
            // what going to go here ?
        }
    }
});

$('#table').dataTable({
    "aoColumns": [null, {
        type: 'date-eu',
        targets: 0
    }]
});

HTML

<table id="table">
    <thead>
        <tr>
            <th>Normal</th>
            <th>Image</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td>5</td>
            <td data-order=2>
                <img src='http://t1.gstatic.com/images?q=tbn:ANd9GcTU-gTaS7b67Ii3MMFaIRNQBdCinr9tNrU31GakpQGq9zok7cjKFg' />
            </td>
        </tr>
        <tr>
            <td>-</td>
            <td>-</td>
        </tr>
        <tr>
            <td>10</td>
            <td data-order=1>
                <img src='http://www.fancyicons.com/free-icons/112/must-have/png/16/stock_index_down_16.png' />
            </td>
        </tr>
        <tr>
            <td>20</td>
            <td>-</td>
        </tr>
    </tbody>
</table>