It's not yet possible. But that might be possible in the near future.
Here is the latest official statement from Pjotr on that topic:
http://www.shipsim.com/ShipSimForum/index.php/topic,1071.0.html
"Static objects
Adding scenery objects and static ships is a whole lot easier. We encourage users with an interest in 3D modelling to create objects like ramps, jetties, static ships (to be moored or anchored), wrecks, icebergs etc. Initially, you can send these to info@shipsim.com in the 3DS format, with accompanying texture in DDS format. Later, we may extend the mission editor to automate the process for adding static objects."
Regards
groennegaard
