As an enhancement to fix of bug 134210 I propose the following: The vertical/horizontal flip property of bitmap background of shapes is missing from LibreOffice. Currently we use a workaround in import filters, we flip the bitmap in import time. Then when we export the file, we export the flipped bitmap which looks the same but is not the same (flipped vs. original + flip property). Let's implement this property properly, for the better interoperability.
Seems reasonable.
Bug 125896 is probably related (interestingly the workaround doesn't take place there).