Plasma themes rock ;-)
Now you can have a much more consistent look throughout KDE 4. Just us a theme combined with a matching colorscheme and you're good to go.
Here are a few screenshots showing how KDE 4 trunk can look these days.
I must say Slim Glow really is a favorite of mine, it always looks good. For those who wonder how hard it is to install Plasmathemes: ridiculously hard. Really. You have to through at least 3 mouseclicks on weirdly named buttons like "Get more themes", pick one yourself (the horror!) and click "install", then you even have to CLOSE the window... Luckily by then you only have to choose the theme you want to apply and it's done. Boy, when will KDE grow up and start thinking for us silly users? Or at least let us google, then sort through a website, download, locate and add themes by hand. Wait, you can, of course. It doesn't have to be three mouseclicks, it can be needlessly complicated just like you're using Windows ;-)
For those who like pink (and honestly, who doesn't?) here a Fluffy-bunny based look as finishing touch. Respect to the guy/girl who made "Sugarcoma Bunny" (find it on kde-look.org).