Images in Qt show up incorrectly if each line is not aligned to 32 bits.
It is pretty common for an image's lines to be 32-bit alinged by chance.
Obviously any 32-bit image will not have any problem.
For the bug to manifest itself you'd need...
* a 1-bit image whose width is not a multiple of 32
* an 8-bit image who width is not a multiple of 4
Testing more images now and added a 7x13 png test image