Hi Srutibox and Droneo fans!
I've been a little remiss giving out tips for interesting drones, so here's one now:
I've been making thick textures using either of these programs by setting two or three reeds to the same intervals and turning on the random feature, and adding some chorusing. Bt using the churn feature and setting both voices to something similar (or the same for that matter), but with a different mix of reeds, you get a very nice movement going on.
Droneo users can get added movement by using the Evolving voices for this. I think I spent about an hour listening to an Evolving 4 patch set up this way .

The drone apps are really pretty powerful and flexible... while the individual reeds have strictly harmonic partials, there's nothing to keep you from setting up a few reeds to fill in the inharmonic partials.