Library names under (scheme ...) i.e. R7RS small and large:
https://registry.scheme.org/#library-name-scheme

Character names now have string escapes and Unicode codepoints:
https://registry.scheme.org/#character-name

A lot more # and #! syntax, and notes about where it's from:
https://registry.scheme.org/#hash-syntax
https://registry.scheme.org/#hash-bang-syntax