Well, to be honest, I'm not to keen with the quotes concept in general, but If you like to stick with it, I'd suggest to display one quote per day or hour instead a random one per page refresh.
Instead of Wikiquotes, how about a tip of the day, i.e.
"Tip of the day: Indigo includes a huge metal material library. [link to NK database in the manual]"
or
"Tip of the day: Did you know Indigo is free?

"
You could gather those tips from the forum veterans as you did with the former quotes. A tip of the day would be useful to new users and it certainly would get me more interested as a first time visitor than some random guy telling me how great that piece of software is (which automatically makes me wanna locate the "Buy now!" button.)