I learned trestle board as the monthly newsletter and as the Holy Bible. In one case the plan of action at lodge for the month. In the other case the plan of action everywhere for life. In both cases we work based on the designs on the trestle board. I learned tracing board as the crowded pictures that get posted all over the building. I take it what you mean is what I learned to call tracing boards. Fun variation in terminology.
Tracing boards come in a few forms. Most show all of the hieroglyphic emblems of a degree or of all three degrees. Many show the familial relationships among the appendent bodies and the lodge degrees (since the Shrine dropped SR/YR requirements these now show obsolete diagrams). Some show past activities or well known members.
Compare the ones with the hieroglyphic emblems to the long form of the degrees. You should be able to go through the picture using a specific pattern and encounter every symbol of the degree or degrees. These are a "valuable aid to the memory" without having any words in them. Yet a picture is worth a thousand words! With short form lectures, reduced degrees, monitorial verbiage being optional, these pictures tend to have more symbols than our current memorized work include.
The ones showing many appendent bodies describe what you need to do if you decide to join one of them and in some cases have a summary of what you will learn in some of them. The common one showing a staircase on each side give very brief summaries of each degree of York Rite on one side, Scottish Rite on the other side. Again a "valuable aid to the memory" this time only giving the name and symbol of each degrees.
The ones I find the most instructive and the least obvious are the ones showing historical scenes. Maybe it's a painting of George Washington laying the cornerstone of the US Capitol building - Keep looking and you will find more ad more symbols, more and more allusions, more and more history in these paintings. Or a painting showing King Salomon's Temple with the land around it and people in various locations - Keep looking and think about the third degree.
But maybe it's a picture of the lodge members doing an apron march at a civic event. Those pictures give direction as to what events worked well in the past and are therefore hints at what events should work well now. They are events loved well enough to go into the archives of the lodge and be kept on display in the anteroom. Or maybe it's a certificate of a time the lodge won an award for excelling in a ritual competition or for sponsoring a kid's event or whatever. Do you see those certificates as records of times past or do you see them as challenges for your year in the east? Just sayin ...
