Currently, there is Project: Sea Serpent going on, which is coming to an end. What is it? It is a project I, Steriaca, have started to show some love to the extremely neglected class of monsters, the Sea Serpents. Evey contributor is free to add a created card to the project (there is no time limit, or quantity limit), so feel free to do so. We also have Project: Heart Of The Cards, Project:Naruto, and Ultimate Chaos, a booster pack that only uses made-up cards.
There may be other projects at a future date (like, say, Project: Konami). Feel free to submit your own project.