We had a little discussion on the Octave Maintainers list. I thought maybe there would be strong feelings either way, but that turns out not to be the case.
* The logo can either be a mathematical surface like the Octave sombrero, or a hand-drawn clip art. Nobody is strongly in favor if either one, but I really want the logo to be reconizable even when tiny, so I'm leaning towards a hand-drawn one, but you're the artist, so you decide.
* While I asked you for an Octave Workshop series of logos, these logos may also be used for Octave itself. My personal opinion is that, on the splash screen, it should say "Octave Workshop", but the logo itself could be the same.
* There is interest in SVG logos, although I may need ones that are rendered to PNG for the web page and perhaps also for the application itself (I'm not sure how SVG works in QT.) I don't know if SVG->PNG needs to be tweaked for tiny icons, you're the artist.
* These logos should look at least as good as the anonymous clip art I'm using right now.
Ideally, you could show us a few ideas and then we'd pick one you would then refine.
Well, it's your project now. Show us how to do it.