There is a balance between some of the things a community may want and giving STEEMPEAK users a consistent social media experience.... but with that said. We already let users change TOP IMAGE so that's a pretty common expectation.

Adding a few features or even removing features seems like a function decision and an easy thing... however changing the whole appearance or color could be problematic decision. I think maybe if you're saying the community could have a Preferred Customization default then maybe that's cool.
But only if they realize the END USER chooses how they want to see the page anyway. So they may have a STYLE they prefer to keep their experience constant across several communities.