In this article about the Linux Sampler they make reference to some interesting soundfonts that I think we could use in Renoise. The Versil Studios collection and the Flame guitars are very nice quality.
There are several sources for free and open source sound banks in all of these formats, including the Virtual Playing Orchestra project, the Versil Studio collection, Flame Studios guitar samples, and many more. You can also purchase bundles of Gigasamples from a number of sample bank companies. As long as you have Linux Sampler, you have a way to play Gigasamples, Soundfonts, and SFZ files.