I found how to change the BackgroundImage of the ToolStrip programmatically using a resource from the global resources file (Resources.resx)
I just want 2 share it coz I'm nice (well, I might find it here again after I will 4get it shortly...)
inspired by this post...
And this is how:
ToolStrip_Shortcuts.BackgroundImage = (System.Drawing.
Bitmap)global::GUI.Properties.Resources.ToolStrip_Background_Blue;