How do you base your community project is up to you, but of course as I mention in all my blogs, the core are the people.
For example if you want to base your community when photography is involved, of course the main topic of your community you will take on images they take or which you want to represent. But when you want to involve your community work they are the best solution although it’s not always the best decision to base your feedback on images only. But you have to choose a core.
Deviantart is a good example of community which is really complicated. It’s based on images and on text as well. In fact it’s a community based on creativity itself. It is a product of a years of work and hard dedication. And not only of staff behind it, but a huge amount of feedback and work as well was done by contribution of community. It would’ve never made without it.
Another good example I have is just to show how quickly you can exploit a market targeting privileged. Is for every one well known Facebook. First they invited students from Oxford only what made their Social network privileged. And then I don’t even need to tell how they followed. Of course it was made functional and functions like tagging in my imho made it very attractive, but marketing made a very huge role in granting first market share for the company. As in Deviantart example we can see that it was made to serve purpose and grew from it.