You can find numerous sites on the Internet where you can download themes for Windows XP. Unfortunately you need to run some shareware in the background or patch the official uxtheme.dll that comes with Windows. Since, I'm already burning CPU cycles and memory running a firewall, an anti virus and an anti spyware tool, I'll go for pactching the DLL.
But hey... that doesn't give me any new fancy icons!? What do I need to do for that? Another shareware tool? No thanks. Any free alternatives? Not realy, because they only allow to change a limited number of icons. You need at least 2 tools before you're able to change all icons (desktop, drives, file types,...).
So in the end I decided to continue using the Luna VX theme. And I'll stick with the standard Microsoft icons for now.