Use CSS to define desktop notification image and use a PNG instead of ico.

src/styles/global/_base.scss

@@ -60,3 +60,7 @@ a {
 .dialog-header-confirm {
   background-color: $dialog-header-neutral;
 }
+
+.desktopnotify-icon {
+  background-image: url("../img/notify.png");
+}

static/js/services/desktopnotify.js

@@ -18,10 +18,21 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
-define(['jquery', 'underscore', 'desktop-notify'], function($, _) {
+define(['jquery', 'underscore', 'desktop-notify'], function($, _, notify) {
 
 	return ["$window", function($window) {
 
+		// Retrieve URL from CSS.
+		var defaultIconUrl = (function() {
+			var iconElement = $("<span>").addClass("desktopnotify-icon hidden");
+			iconElement.appendTo("body");
+			var url = iconElement.css('background-image');
+    		url = /^url\((['"]?)(.*)\1\)$/.exec(url);
+    		url = url ? url[2] : "";
+			iconElement.remove();
+			return url;
+		}());
+
 		var helper = notify;
 
 		var desktopNotify = function() {
@@ -86,7 +97,7 @@ define(['jquery', 'underscore', 'desktop-notify'], function($, _) {
 
 			var opts = {
 				body: body,
-				icon: "static/img/notify.ico",
+				icon: defaultIconUrl,
 				timeout: 7000
 			}
 			$.extend(opts, options);