k-grid change button appearance

HTML

<script src="http://cdn.kendostatic.com/2012.1.322/js/kendo.all.min.js"></script>
<link rel="stylesheet" href="http://cdn.kendostatic.com/2012.1.322/styles/kendo.common.min.css">
<link rel="stylesheet" href="http://cdn.kendostatic.com/2012.1.322/styles/kendo.metro.min.css">
<div id="grid"></div>

CSS

span.k-delete {
    background: url("http://i.minus.com/jBi2zVdXuHBaC.png") center center;
}
.k-grid .k-button-icontext .k-icon {
    margin: 0;
    vertical-align: middle;
}
.k-grid tbody .k-button {
    min-width: 50px;
    width: 22px;
}

JavaScript

var crudServiceBaseUrl = "http://demos.kendoui.com/service",
    dataSource = new kendo.data.DataSource({
        transport: {
            read: {
                url: crudServiceBaseUrl + "/Products",
                dataType: "jsonp"
            },
            update: {
                url: crudServiceBaseUrl + "/Products/Update",
                dataType: "jsonp"
            },
            destroy: {
                url: crudServiceBaseUrl + "/Products/Destroy",
                dataType: "jsonp"
            },
            create: {
                url: crudServiceBaseUrl + "/Products/Create",
                dataType: "jsonp"
            },
            parameterMap: function(options, operation) {
                if (operation !== "read" && options.models) {
                    debugger;
                    return {
                        models: kendo.stringify(options.models)
                    };
                }
            }
        },
        batch: true,
        pageSize: 30,
        schema: {
            model: {
                id: "ProductID",
                fields: {
                    ProductID: {
                        editable: false,
                        nullable: true
                    },
                    ProductName: {
                        validation: {
                            required: true
                        }
                    },
                    UnitPrice: {
                        type: "number",
                        validation: {
                            required: true,
                            min: 1
                        }
                    },
                    Discontinued: {
                        type: "boolean"
                    },
                    UnitsInStock: {
                        type: "number",
                        validation: {
                            min: 0,
                            required: true
                        }
                    }
               ...