Most of what I can see is not unusual. I am sure Kendal will comment later. He's drained more tran-axles than I. As you know the particles stuck to the magnets contain iron and will be there from normal gear wear. I have seen some iron chucks stuck to the magnet maybe created from a missed shift / gear grind.
Some of the aluminum would be from the original milling , machining and drilling that didn't get flushed out or blown out before assembly.
As far as the seal material. it could be from a number of places . Has the car ever had a tranny cooler? There are seals at the out put shafts. Small O-ring at the speed sensor. There are three taps on top of the tranny for the breather and circulating lines.. I would clean all the filters, plugs, magnets etc,.. remove all of the fluid and use all new fresh fluid. If the Trans-axle is not leaking any where and it is shifting fine I would not be concerned about the debris.