When we propose new Logos on our Beta sites - what are the constraints on it? Maximum dimensions, colors, etc? There must be some limits, but the only closely relevant Questions I have found(Uniformity of Logos, Who designs the Logos?) have no details.
It's just a tad bit early for us to provide a an accurate answer. Jin, our resident awesome designer, is in the process of mocking up the basic layout that will brand each of our sites. It's simply too early to say how the logo will fit into a design-in-progress.
In the meantime, I would suggest focusing more on logo ideas and basic design concepts rather than a finished sample. If the idea is good, it can be morphed/squeezed/reworked into something that fits the criteria.