Ok guys this isn't a big step but at least a little bit of customization:
Using rom toolbox from market:
Just switch to interface tab and select the start animation settings. Now you should have a good variety of animations to choose from.
The manual way:
How to create/change the bootanimation:
1. get a fitting bootanimation.zip either by searching in the xoom dev forum (didn't try bootanimations created for other devices)
or create one yourself (google will help you with that)
2. paste this file into /data/local/ (this doesn't need root)
alternatively you can pasteur it to /system/Media (needs root) but be aware, this file should be untouched because it can work as backup if you screw things up
3. Change permissions e. g. in Terminal Emulator 'chmod 644 bootanimation.zip'
4. reboot and watch awsome new bootanimation
Thanks to luke.arran for checking out the rom toolbox setting ;-)