What do you consider useful stuff that the Board could do, and how does it compare to the (in my opinion) very valuable work of teachers, translators, artists, learners, and people involved in defining the language (e.g. BPFK)?
The reason that LLG exists is to serve the teachers, translators, artists, learners, etc. In the words of the bylaws:
The Logical Language Group, Inc. shall place priority on support of the community of persons learning, using, experimenting with, and promoting the language known as "Lojban - A Realization of Loglan" or alternatively "Lojban".
The board exists to represent the members of the organization whenever they are not meeting as a formal body, and so it has the same purpose, but higher expectations of participation.
An excellent reason for people to get involved with LLG, either at a membership or director level, is because they have ideas about how LLG can better support the lojban-using community.
da poi ctuca gi'a fanvi gi'a finti gi'a cilre zo'u pe'i la lojbangirzu va'o po'o lo nu da se sarji vo'a cu vajni