Thanks to the newest site update, we now have the tools to moderate clans, including banners.
Clans with obvious trolling banners (paint-drawn penises, portrait photos...) will lose their rights to a banner, and will have to purchase them again.
Clans with banners that we deem ugly will have the current banner removed. If they upload the same banner again, they will have their banner rights removed.
There are no specific guidelines about what we consider ugly, but as a rule of thumb you should avoid anything that stands really out of place (photos, fluorescent colors, modern fonts, plastic-looking banners...). If you are unsure whether your banner is acceptable, come ask me or other moderators in IRC.