ICO is an image file format (associated with ".ico" file extension) developed by Microsoft and designed for storing icons
PNG (Portable Network Graphics) is an image file format designed to store raster graphics
However ico files if stored properly are not significantly larger than png files because since windows vista ico files can store png
Favicon format GIF or ICO?
Your icon file should be icon type not png may be because png is not supported by cx_freeze;in your setup.py change to please note the icon file must be in ico format don t act smart and just change the extension
Python crashes when trying to compile using cx_Freeze