The extra image format handlers are distributed as Qt plugins, but it appears that Qt is not able to find them despite the presence of a qt.conf file. We'll get that fixed for a future release, but in the meantime you can workaround the issue by setting the QT_PLUGIN_PATH variable in the environment. For example:
export QT_PLUGIN_PATH=/Applications/Canopy.app/appdata/canopy-1.3.0.1715.macosx-x86_64/Canopy.app/Contents/plugins
[edit]
Actually the plugins fodler is properly found after the application object has been created:
>>> from PySide import QtCore, QtGui
>>> app = QtCore.QCoreApplication([])
>>> import pprint
>>> pprint.pprint(QtGui.QImageReader.supportedImageFormats())
[PySide.QtCore.QByteArray('bmp'),
PySide.QtCore.QByteArray('gif'),
PySide.QtCore.QByteArray('ico'),
PySide.QtCore.QByteArray('jpeg'),
PySide.QtCore.QByteArray('jpg'),
PySide.QtCore.QByteArray('mng'),
PySide.QtCore.QByteArray('pbm'),
PySide.QtCore.QByteArray('pgm'),
PySide.QtCore.QByteArray('png'),
PySide.QtCore.QByteArray('ppm'),
PySide.QtCore.QByteArray('tga'),
PySide.QtCore.QByteArray('tif'),
PySide.QtCore.QByteArray('tiff'),
PySide.QtCore.QByteArray('xbm'),
PySide.QtCore.QByteArray('xpm')]
>>>
But the svg format still seems to be MIA. I'll check into that further.