In the CVS are the source files for the windows installer. So everyone can create his own, I think most people would like to change the bitmap (PythonPowered) and use a more specific bitmap for their package.
I would happily accept a better (general) bitmap!
Creating the installer executable is not the problem, but to use it you have to change bdist_wininst.py. (If you only maintain one package this is not a problem but if there are more, you had to change it everytime you want to create an installer for the other package.)
Recompiling the installer executable only to change the bitmap seems overkill to me. You could use win32api calls (if available) to replace the bitmap in the executable without need for a compiler, better would be to pack the bitmap into the installer archive at runtime. This could also be done on Linux.