Not sure wether to call it a bug, but in ooo_custom_images/oxygen/res there are still several OpenOffice.org icons, and once the source is built and run with the Oxygen icon set, the main window shows up with the old icons. It doesn't happen with the other ones, which correctly use LibreOffice's icons
Confirmed. I'll fix it. Thanks for the bugreport.
fixed for 3.5