Reusing logo and documentation pictures for such usage seems fine to me. I would personally mentioned for the doc pictures where they come from.
This page seems to be describing allowed usage for the logos and other Apache trademarks:
On Fri, Jan 04, 2013 at 01:28:00PM +0900, Juhani Connolly wrote:
> Myself and a colleague will be doing a presentation/usecase on flume
> at "Hadoop Conference Japan 2013 winter", trying to get it more
> awareness here. Is it reasonable to reuse the logo within the
> slides? How about diagrams from the docs? I'll be sure to post the
> slides here after the event, though they'll be in Japanese so
> probably only useful to a handful of people.