You are allowed post about your game in the "Show off your project" forum. The post should link to where your game can be downloaded or hosted (itch.io, steam, dropbox, etc.) but there is not a good way to have the downloadable package attached to your forum post. 

If you are asking about making an art submission, then you may share the game's assets as an art submission, and you may include a playable game along with that submission, but the downloadable package should be arranged such that the focus is on the game assets and making those assets reusable and easy to access. The playable game component should be secondary to that.

Submitting just the game without any openly-sharable and reusable game assets is not allowed.