Additional languages will come, but we're starting with Node.js. We'd rather take the approach of doing one language really well than a bunch of languages with a poor developer experience.
Image magick's binaries are already installed on the image. Any native binary node module that has a preinstall script should work too. If you hit an unsupported syscall error, contact firebase support at firebase.google.com/contact/troubleshooting and we'll triage.