libpng warning: interlace handling should be turned on when using png_read_image in Python/PyGame

I had the same problem. It seems to be some bug of older libpng versions (see http://sourceforge.net/p/libpng/bugs/165/ for detail).

It should be already fixed, but not in my current setup: win32 + python 2.7.3.

As a workaround I simply converted png-24 images to png-8 in Photoshop and message has disappeared.