Essentials would be the famous LJ-Cut. You should use it when including an artwork in your posting. Like that you can avoid some computers to crash. Not everyone has a fast web-connection and they might become angry when your 300 KB image seems to load forever.
Grab an LJ-cut and hide your image behind it. It´s for the better, believe me.
If you don´t know how to create an LJ-Cut, you can read the Livejournal-FAQ for this particular topic.
Now, a certain Etiquette is essential, too. We all share a particular interest, have something incommon.
So we should feel a connection between all community-members and not flame or spam them. Please hit the "post to community"-button only then, when you have something spiffy to show here or of course, if you want to leave some nice comment and/or review to an artwork somebody has contributed.
i've already made some tags, the tags have been created to allow users to find better search results when visiting this community.
Please use them!
if you feel that a tag is missing, please feel free to write a mail to lhenya.
Speaking of comments:
Please do not overtake silence here, and take a sec to always leave a comment on stuff people have posted. Feedback is lovely food for artists. It only takes some seconds to write a short note and hit the button...