FYI
According to Roberts Rules (revised version), everyone on the Nominating Committee can be put on the slate presented for a vote. If this were not true, then you could prevent someone from running for office by making them a member of the committee.
Our By-laws state that two parents and two teachers (staff) can serve on this committee. No Board members on the current board but nothing about a former officer.
Our bylaws require that a current officer (or last year's president) be one of the 4 members of the Nominating Committee. In practice, we select one of the officers who is not planning to run again. The other 3 members must be from the membership at large. Our bylaws don't stipulate whether or not the members of the NomComm can run for office, though it would be awkward if they did (would probably resign from the committee first).
It depends what your charter (by-laws) say. Ours says that a board member can't serve on the nominiating committee (which is chaired by the Principal). It also says, that anyone serving on the nominating committee is ineligible to run for office. Of course the year we had problems filling spots was the year we had a nominating committee member resign to fill the hole.