I don't think there's any reason to get knickers in a knurl at this point; just pick something for the moment which is *not* a trademark (so, ixnay for the Wikimedia variants logos for the moment) and you'll be fine. Once you have an official chapter status you can shift to any of the very nice Wikimedia logo variants; I kinda like the logo with the leaf replacing the dot.

Biggest thing: pick something you like, even as a 'placeholder' logo. It's gonna get stuck on a lot of things; pick something you'd like to wear embroidered on a polo shirt. If you wouldn't want to wear it, you're probably not too interested in supporting it.

Amgine