Plurk I can't help with so much since I don't have one personally. But overall design for a musebox is up to you. Some people love to be fancy, others are fine with defaults. All that matters is that it has what you want it to have since it is your personal spot to play with people you invite, so some people may find some things useful that others have no need for. A muselist is good to have, and you'll obviously want posts to play in. Some people also have posts to keep tabs on their verses and PSLs (basically the different types of characters, with one character you may have different settings you play them in, that's a verse. And a PSL is a private story line).

For a muselist, all that is really absolutely needed is the name of the character, what canon they come from, what their journal is, and any games you play them in. Nothing wrong with a text only list, my own is and very out of date at that. But if you want to make it pretty, that's fine as well.