One recommendation I have given before for Berlin is the Sorat Art 'otel.
See Zine message 19903 of 10 March 2002.
There is also a referral from Linda, message number 19892, of the same
date, with some web page references for an alternative hotel.
They are not B&Bs but may have some attraction for you, if you check the web
pages given in those messages.
Although I really enjoyed my time in Vienna, I wouldn't recommend any of the
places that I saw or stayed in. Other Ziners may be able to help.
Best of luck.