The best way to update the main page is to set up a copy of the page under something like "Main Page/MyRedesign", edit it as much as you like, get it reviewed when ready, and then Urwumpe or myself can apply your changes to the real thing.
To set up such a page, you'd click on the protected page's "View Source" link and copy that to clipboard. Next you manually add "/MyRedesign" (or whatever you like) in the browser's URL bar. You'll get a blank page and a "Create" link. Just click that link and paste the source you copied. Save.
The Main page is a bit tricky in that it includes several other pages, but you can just apply the same trick to all of them. For example, OrbiterWiki
ilot_section: navigate to that page, copy the source, add "/MyRedesign", paste the source. Now to back to MainPage/MyRedesign, and find all references to Pilot_section (there are two). Append MyRedesign.
Etc.
To test that all this works, I've logged in as a Test user and set up this:
http://www.orbiterwiki.org/wiki/Main_Page/Redesign - note the "Pilots" section has changed. You're welcome to just edit this "/Redesign" stuff I've already created, but you'll still need to apply the trick to the Developer, Contributors, etc sections in order to modify them.
Regarding the logo: the current one was custom-made in 2005 or so. If someone comes up with a nice replacement that others like, we can use that instead. Same goes for the skin, but it's harder to get people to agree that a new skin is nice...
P.S. I don't edit much on OrbiterWiki, but I look at every edit since that's the only reliable way of catching all spam. So if you edit my Talk Page there (
http://www.orbiterwiki.org/wiki/User_talk:RaMan) I'll definitely see it. I'm certainly open to any requests that help make OrbiterWiki more useful, admin/server-side things in particular.