There aren't many rules and you are free to submit anything you want as long as it follows these rules:
All art submitted must relate to conlangs/conworlds
Respect the intellectual property and rights of others
dA Resources for Your Conlangs
Conlanging: A How-To
A crash course in linguistics for people who want to create languages for their pieces of fiction.
A Rosetta Stone-like program that you could customize for your own conlang.
Conlang Outline Info - Template
A simple template for outlining your conlang.
Conlang Outline Info - Template 2
A more in-depth template for outlining your conlang
External Resources for Your Conlangs
Random Phonology Generator
Create a Lexicon for Your Conlangs
Zompist Bulletin Board