Basically the title. Floating suspendium islands could come in different sizes for the sake of variation. Maybe with a size limit of 100m or so, before it gets completely ridiculous.
The bigger ones would float higher, because they have more suspendium in them, and so they wouldn't completely block the paths of ships. Ships could also be able to target and destroy the floating islands, or at least chip a sizable chunk off, in case one is blocking the path of a low-flying ship anyways.
I think I'd build a bunch of cheap, small ships with rockets or grenades just to follow the fleet around and blow up floating islands that get in the way, while the actual fighting ships fight.
Also, this could have the potential to make some interesting bottleneck scenarios.