If you own Doom 2, and have an interest in game design, my buddies and I are part of level design team where we design a new custom level pack for Doom 2 every month! The levels are available to download and play for free.
Designing levels is pretty fast and easy, but it's a learning process, and we can teach. There's also a variety of other small jobs we could use volunteers for, such as minor graphic editing, MIDI music composition, and general testing feedback. If creating your own worlds in old-school FPS games and balancing gameplay is something you are interested in, please consider joining our group! Message me for details or respond to this thread with any questions you might have.