With only some additional lines of code it is easy to change the background of your WP entries for each category.
Actually you could even change the whole design for each category and use a diffferent header or sidebar for example. No limitations are set.
The only thing needed to do so is a conditional tag, and of course Wordpress offers that tag.
(in_category())
Using this condition and a classic if, elseif php call we can change everything we want for the categories we chose. The CSS, even the template.
You can use this in the header, using combined conditional tags to define if you want to use this site wide, or just for specific pages, categories or entries.
The background images (closing tags) and background color for several categories I use are easy to achieve.
Open in your theme folder the file index.php or if your theme uses a separate file for the loop, theloop.php and look for following line1

This is where we have to insert our conditional tag and decide what we want to use to create a different background for entries in a category.

As you can see I use a different class in the cascade for every category, but there are no limits for this principle2.
You could easily use this for a totally different entry template (the file single.php) for different categories, in which case your code would look like this

And obviously you can even call a totally different CSS for every categroy, or for specific pages. All based on the conditional WP tags.
1 This how-to is based on Cutline, and not Kubrick or k2. But the procedure is the same for anytheme, the classes might be different.
2 Do not forget to make the needed changes in your CSS!
4 have made me smarter ↓
1 Djizeus // Jan 6, 2007 at 10:02 pm// View all comments by Djizeus//
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That’s definitely a cool tool (and tip). Many blogs that I read would benefit of that.
2 Joefish // Jan 9, 2007 at 5:28 pm// View all comments by Joefish//
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Have you looked at the Sandbox theme? This has that functionality built-in. It moves the voodoo to functions.php to keep the loop clean. Er. Cleaner. Even a clean loop is still a little ugly. Anyway, it will set multiple classes for multiple categories and it uses category slugs instead of ids.
It’s a pretty slick system, and it’s easy to replicate. I use an adapted version of this for my post classes.
3 Franky // Jan 9, 2007 at 5:48 pm// View all comments by Franky//
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I have the Sandbox installed locally, but never really went into the specifics of it.
Problem for me with most of those adaptations I have is that many add-ons don’t interest me.
BTW 1 : Saw you @ testers. :-P
BTW 2 : I hope to manage it before July to move this blog to a new platform. Probably RoR.
I will also follow the Habari evolution. I just like it slick. ;-)
4 Joefish // Jan 9, 2007 at 10:02 pm// View all comments by Joefish//
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I’m really interested in Habari. However, no PHP5 on my webhost yet. I’m definitely watching with interest.