If image field is null in kendo grid and you want to show default image then use this code.It will show default image if image field null.

{
    field: "Photo",
    title: "Photo",
    template: function(dataItem) {
        return kendo.template(
           '<img src="#= Photo #" alt="image" width="100px" height="100px" />'
        )({Photo: dataItem.Photo || 'Add Your Default Image Path Here'});
    }
    width: 100
}