Dont know if its me, but custom addin images seem to b pain in the *$$. Done everything by the book, but no image showing up#@$. I'll stick to the faceid's http://skp.mvps.org/faceid.htm for now. (change the default 54 to the number of your choice)

Command command = commands.AddNamedCommand2(_addInInstance, "OvernightPowerAddIns", "OvernightPowerAddIns", "Executes the command for OvernightPowerAddIns", true,[your number], ref contextGUIDS, (int)vsCommandStatus.vsCommandStatusSupported+(int)vsCommandStatus.vsCommandStatusEnabled, (int)vsCommandStyle.vsCommandStylePictAndText, vsCommandControlType.vsCommandControlTypeButton);