Mac/Amiga/PC CD?
ISO level 2 and 3 can 30.30 while level 1 is 8.3 on filenames. I don't know
of any driver that supports more and 8.3 I guess since Rock Ridge handles
the long filenames up to 255 characters.
You might download the hi-sierra spec in this forum since it is very close
to ISO-9660. The only parts that are different is directory entires and
volume descriptors. (directory and file entries are the same). The format
gives A and D characters which are valid for different things which I don't
recall off the top of my head.
All upppercase [A-Z] is a good starting point.