Might be tricky to implement this one, depending on your database structure, but how about "the last 5 things that happened".
It could say "DaveedBeekham has joined the forum", "benny! has signed in" or "Jim has scored 5982 points on Chain Reaction" or something like that.
The SMF database has a lot of tables, however not everything has a time stamp on it so unfortunately if I was to impliment this then it would have to be limited.. I dont want to be adding fields to the database really if I can help it. Cool idea though! Incidentally maybe something could be done with XML.
How about a 15 second looping MIDI that plays "Dancing Queen" by ABBA?

Go to the back of the class!
A nice shiny logo.
Yes.
I will ask some friends unless anyone knows a >really< good artist?
Definitly hot posts & latest posts, next competition (if any to come).
Things like latest users, who is online, top users (most posts, more karma?), a random arcade taken from the list are also nice.
A java applet or a flash effect could become boring if displayed all the time. Now, it's a matter of taste.
Latest topics, definately, who is online is already implimented so that would be easy enough to do

Compos hmm see below too

There should definately some teaser content for hot
topics in the forum for now - since the forum is the
most used function of the site right now.
So teasing compos, hot threads, new user might be
interesting.
Also, thought about a little flashtro/applet - but this
could be boring if you see it every time !?
Flashtro / Applet, are you offering your services?

Compos again..
Something definately needs to be done here.
Something that encourages new members to post a little bit about themselves.I think yo'll find that once somebody gets over that first hurdle they are more likely to come back to see their replies and play an active role in the forum.They obviously like the site by registering in the first place so if you could come up with something on that first page i think it would make your site even more formiddable.

I will re-install PM on registration to take care of this

I'll make the message extra friendly!
This months additions to the Showcase / Compos should be displayed I think
Perhaps I could even moake a competitions page to show the winning entries off.
The way I'd like you to think about this is a multi-paged portal.
So on the first page it could be;
navigation
recent posts
who is online
shoutbox
Etc Etc..
It can be pretty much whatever we like.