Much like its contemporary DOOM, Escape Velocity has a fairly open-ended game engine which allows end users to replace assets and game data. With tools that where widely available at the time (ResEdit et al) users where empowered to make plugins (what you'd now call mods) and TCs (Total Conversion mods.)
There are hundreds of plugins to try, which may improve (or break) gameplay, alter the game, whatever. They where a unique form of self expression enjoyed by the community.
Because the mac plugins use a Classic Mac OS specific pseudo-database format called a resource fork, the windows port needed to reimplement the data format. In order to use mac (usually .bin or compressed versions thereof) plugins with nova for windows, you'll need to convert the files.
Game data is stored in two directories: Nova Data and Nova Plugins. The game data is read from Data first, then the contents of Plugins overrides it. To install a plugin simply put it in the Nova Plugins directory. Some TCs replace the Nova Data directory (The only exception seems to be Polycon.)
The format for the data files is exhaustively documented in the Nova Bible which I won't attempt to summarize here. But playing with the data files and making the game your own is part of the fun-I'd encourage anyone to try! Available editors include Mission Computer (Mac) EVNEW (Windows, source available) and RezEditor (JVM). Due to technical constraints mac plugins have issues unzipping on other platforms, but the above linked conversion tool can handle entire compressed archives.debugger;
Allows you to run (windows) Nova at different resolitions. Mirrored here. TODO: Create a nova image with this pre-installed.