Hello,
Image sizes in CSS is an interesting question. - Basically you need to ensure that all of your images are as compressed as possible. - But, a new practise is emerging that you do tend to see in CSS Zen Garden where they place one large well designed image at the top of the page - some of them are up to 70k. - This is fine if it is called within the CSS as the text displays first so the visitor can begin reading the page before the image is loaded. - With this technique though they tend to just use the same header for all pages which means that for the inital load there is a delay in viewing the image, but for all further pages the image is already cached so the page loads much quicker. - In your case you are changing the header each time, so you are experiencing a delay each time.
As always I would try to compress the images as much as possible.
I wouldn't chop the image into 1pixel pieces unless you can use techniques where you take an image and repeat it horizontally or vertically.
The main slowness for the site was the very first page load of the site - and that is due to the site not being in your hosting servers memory. - It can take up to 17secs for a server to load a DNN site if it is not in its memory - plus the time for the page to load. - A DNN site stays in the servers memory by being regularly visited.
For instance with the host from DNN Creative, if I do not receive 1 visitor every 10-15mins the site is taken out of the memory until the site receives another visitor. - This is to save server resources.
You can get around this by regularly pinging your website every 10mins, so it will appear as though you are receiving a visitor every 10 mins and your website will now respond much quicker when you first visit the page.
To set this up go to
http://host-tracker.com/it's a free service which monitors your website for you and informs you if your site goes down. - You can set the time period that it checks your site.
Another thing to check is the display in Firefox - the bottom half of the news background does not display and is in a purple colour.
Thanks,