This OpenSCAD script allows you to come up with a random spacecraft, on a 2.5 inch hex base. By specifying a seed value, you'll get the same spacecraft for the same seed each time.
I make no guarantees about printability. You can assume you will almost certainly need supports, though!
If you DO print one of these ships successfully, please let me know, and post your seed value in the comments if the design turned out to be cool!
I've included a few example STL files of the things it creates. It looks like in my testing, the Customizer can take anywhere from 1 to 16 minutes to create one of these spacecraft.