There is a lot to say about the meeting, too.
In the advice category: you, dear junior faculty, tenure supplicant that you are, are responsible for your own career. The department can provide you with poor mentorship, but bitching about it (particularly in your tenure dossier) is A Bad Idea. As my mother would say: try to imagine how little I care. Saying that “no one told me I needed X number of publications” will carry no water up the hill. Having a change in dept chairs, with a concomitant change in department tenure standards may be worth noting, but do not Make A Big Deal Of It. Appealing the college level decision because “I really worked hard and no one appreciates how hard it was for me” ends up reading like an insult to those who did get tenure. If there is something specific outline it in your letter, make the case for it.
If you do appeal, it is ok to get some letters from people. The committee will know that you solicit these letters, so make them more than the standard “Asst. Prof. X walks on water”. If possible get the letter to directly addresses the aspects of your record that were found wanting. You can send information to the people writing the letter, and say, for example “they felt my publications were in sub-standard journals because they IF’s less than 3076”. Say to your letter writer: “could you address the importance and significance of the journals in which I published, beyond their skimpy 10.2 impact factor?”
If you have been criticized for not being collaborative, then find a collaborator or three to write a letter about the importance of your collaboration with them to them. If you have been criticized for not doing good service, find someone with whom you sat on a committee to talk about the quality of your contributions to the process or project.
You get the idea. If you are going to fight back, as is true for response to editors or grant reviewers, be respectful, no whinging, and stick to the facts. Know what the rules are. Sometimes an appeal will work.
For those not in the slot to go up soon, figure out the rules NOW.