Image Gallery module is used in Parallels Presence Builder (PPB).
'Store my images in Picasa' is chosen and an image is not stretched in a browser on a publishing side.
If 'Store my images in Parallels Presence Builder' is chosen, then an image is stretched properly.
See the difference:
This is considered a software issue. The internal request ID is PPB-4316.
The issue has been fixed in a Parallels Plesk 12.0.18 MU#29. Please make sure that all MUs are installed.