Couple things. Some are things that others have already mentioned.
- Definitely need a top header image. I think that's all the visual customization necessary, but one image can quickly let a user know what a community is about.
- Definitely think posts in Communities shouldn't show up on your blog by default. Appics should just be in Appics, 3Speak in 3Speak, and if you want to share it on your blog, let that be a separate option.
- One thing I'd been thinking about it the idea of a Community within a Community, or a sub-community. Thinking about something like Appics. That's an entire app, and I'd want to be able to see a community JUST for Appics posts and have that NOT posted to my blog by default, but I'd also like to just be able to see art posts in Appics. Maybe this is done just with tags, but I think it would definitely be useful and something users would want.
- As for Community searching, I think it would make sense to be able to define a set of keywords associated with a community, and have search make that community pop up if those words are searched for. For example, say I make a Community about digital art. I could then have some associated terms to go with that like (digital, art, photoshop, painting, concept, 3d, corel, painter, visual, development, effects, drawing, sculpting, zbrush, maya, 3dsmax, houdini, sketch, doodle) etc, you get the point.
Would love to get some early access and throw around ideas with you guys!