Nice Entity is not the single defining resource for entity reference. With so many entities in existance, it's an impossibility to effectively catalogue and represent every single thing!
With that being said, here are some other great sites for character entities. If you find this site lacking an entity you need, chances are one of these other websites has a listing for it.
Extensive Unicode reference.
Worth checking out the rest of the site for other good entity lists.
Good general list of entities.
Very extensive, categorized lists of pretty much all commonly used entities.
Brief list of common entities with Unicode values included.