I have added some new guidelines concerning custom covers. Basically, custom covers are OK, and encouraged where needed 🙂 -But we should also avoid creating too realistic-looking custom covers (which look like they were sold in stores). A new __custom_cover field is also used to register that the cover is an unofficial one. Read more about it at the bottom of this page (section “Custom Covers”).
The cover guidelines have also been moved to its own page.