Just a note to let you know that it is no longer necessary to use
wxNoRefBitmap when assigning bitmaps to toolbars and such. wxWindows is no
using reference counting internally for bitmaps and other GDI objects so we
no longer have to worry about python deleting the object before wxWindows is
done using it.
For the next release I will make wxNoRefBitmap be an alias for wxBitmap, but
until then using it will cause a memory leak so if this is a concern for you
then you should switch to using wxBitmap instead.