Perhaps it's time for Indymedia to move to a cloud computing service such as Amazon's EC2. I imagine it becomes quite a lot harder to sieze a server in this kind of environment. Their server could be running pretty much anywhere (and would easily be restartable,) and their data could be replicated in multiple geographic locations.
Of course, the police could just get Amazon to shut down their account instead. It depends on whether the siezing of the server was to recover data, or to take down the service.