Do not submit to the "Featured" folder.
Do not submit sprites from pre-existing games. This includes traces, bases, edits or recolors of existing sprites. As an example, you would not submit edited RPG Maker sprites.
Do not submit non pixel-art content. Read the PixelJoint Pixel Art Tutorial for clarification.
Submissions to the "Sprite Game Requests" folder must be a well-organized effort to find art for your game. They can be commercial, noncommercial, paid or unpaid.
Enjoy the club! After all, we're all here to have fun!