When Visual Styles are disabled in Vista (and later) Aero Wizards and the Windows Explorer use some kind of reserved image for the back (and forward in Explorer) buttons.
I've taken a look around and seen the resources located in a few executables, but I don't think it's advisable to do LoadImage like that (like if the resource changes in future). I've noticed there also isn't an OEM Image defined in WinUser.h for the fallback back and forward buttons.
I ask this because I'm implementing Aero Wizards in .NET and want to remain faithful to the reference implementation. (although the released specification for Aero Wizards uses the XP back button as an example image).