To add on top of what unSpawn has mentioned. The one thing I've learned about designing websites is the layout and how the graphics fit.
You don't need alot of pretty graphics to make a site look great, but great graphics do make a site look pretty. I've learned though the best looking sites have a good balance of graphics and layout, not too much and not too little. Also placement and layout though to me are the number one thing to making a website nice looking.
If it was my site personally, I would drop the wood banner at top, or at least fade it out, darken the contrast of it or something along those lines.
I would also find a different background for the page, its cool but I think its a bit much. The transparent tables and such are a nice touch, if you can find another background to play nicely with it, it can look way cool.
No offense to the phpnuke peeps but their layouts are getting popular, it looks like a thousand other sites I've been too that also use phpnuke, just a different theme. I'd suggest trying to create your own theme or the liking. Good graphics can even make a sloppy coded site look great.
My advice though if your going to design and maintain websites is to learn the basics of creating and editing graphics.
Also browse other sites, they will give you ideas for your own site.
Another thing I also agree with is simplicity, too much is overwhelming to me and just makes a site ugly. Take example my personal site,
www.trickykid.org
I am still working on it but what I have so far is just simple, decent graphics with a simple layout I made. Even though some will tell you that gray background is boring, I prefer it as its easier on the eyes and such instead of those sites that have a white background that blind you staring at it too long.
Hope this helps.