These are adapted from another forum I used to be a senior member of. Revisions are certainly up for discussion, but I can't help but feel rules on a board full of bronies is going to be a waste of time anyway -- don't prove me wrong!
--avatars may be up to 100 pixels square
--signatures should be a reasonable size that does not disrupt the flow of threads
--avatars, signatures, posts, and private messages are all subject to the following rules
--moderators will remove content that breaks the following rules
--failure to use proper English (no txt tlk, 1337 speak, oR tHiS bUlLsHiT)
--flaming or abusing users (this includes flamebaiting)
--attempting to bypass word censors
--posting offensive content (includes content of a racist, lewd, or threatening nature)
--posting illicit content (warez, copyrighted materials, etc.)
--posting explicit content outside the Explicit section
--impersonating a mod
--three (3) or more Warnings in a 90-day period (1 week, resets Warning counter)
--posting another user's personal information (includes first name, last name, phone number, address, email, alternate handles) without permission (suspension pending ban)
--reversing a mod's edits to your post content
--three (3) or more Suspensions in a 180-day period
--being a spambot
--attempting to circumvent punishment
--The above rules may be amended at any time if deemed necessary by staff, and are not meant to be all-inclusive -- use common sense when posting.
--Repeat offenders will be escalated immediately (i.e. user is warned for posting threatening content, user posts more threatening content, user is immediately suspended).
--A suspension or ban issued for an action not expressly identified in the rules must be vetted by a second staff member.