Kludge to force nm-applet icon size to avoid annoying resize flicker on redraw. Applies to 0.9.6.4, YMMV, etc. Adjust height/width as desired. I chose '20' to match the height of my top wibox bar in awesome-wm.

icon-fix.patch

From d156ce54795695c5308f49fb5e741b5d52ef29a7 Mon Sep 17 00:00:00 2001
From: Will Dietz <w@wdtz.org>
Date: Tue, 15 Jan 2013 11:30:50 -0600
Subject: [PATCH] Kludge to force applet icon size to avoid annoying resize
 flicker.

---
 src/applet.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/applet.c b/src/applet.c
index 6770529..c5a82a8 100644
--- a/src/applet.c
+++ b/src/applet.c
@@ -2152,6 +2152,7 @@ static void
 foo_set_icon (NMApplet *applet, GdkPixbuf *pixbuf, guint32 layer)
 {
 	int i;
+	const int width = 20, height = 20;
 
 	if (layer > ICON_LAYER_MAX) {
 		g_warning ("Tried to icon to invalid layer %d", layer);
@@ -2172,9 +2173,11 @@ foo_set_icon (NMApplet *applet, GdkPixbuf *pixbuf, guint32 layer)
 
 	if (!applet->icon_layers[0]) {
 		nma_icon_check_and_load ("nm-no-connection", &applet->no_connection_icon, applet);
-		pixbuf = g_object_ref (applet->no_connection_icon);
+		pixbuf = gdk_pixbuf_scale_simple(applet->no_connection_icon, width, height,
+                                     GDK_INTERP_BILINEAR);
 	} else {
-		pixbuf = gdk_pixbuf_copy (applet->icon_layers[0]);
+		pixbuf = gdk_pixbuf_scale_simple(applet->icon_layers[0], width, height,
+                                     GDK_INTERP_BILINEAR);
 
 		for (i = ICON_LAYER_LINK + 1; i <= ICON_LAYER_MAX; i++) {
 			GdkPixbuf *top = applet->icon_layers[i];
@@ -2185,7 +2188,7 @@ foo_set_icon (NMApplet *applet, GdkPixbuf *pixbuf, guint32 layer)
 			gdk_pixbuf_composite (top, pixbuf, 0, 0, gdk_pixbuf_get_width (top),
 							  gdk_pixbuf_get_height (top),
 							  0, 0, 1.0, 1.0,
-							  GDK_INTERP_NEAREST, 255);
+							  GDK_INTERP_BILINEAR, 255);
 		}
 	}
 
-- 
1.8.1.1