The formatting is simple enough. Each Pokemon gets 16 bytes. One for species, then one for level, then eleven for nickname, followed by three nulls. Any leftovers in the nickname are filled with end-string characters (hex 50).
The HoF data pictures will display:
A level 6 Charmander named CHARMANDER
A level 12 Rattata named Mutton
A level 4 Rattata named AAAAAAAAAA
A level 3 Mew named MEW
A level 40 Cloyster named NAUGHTY
A level 21 Magikarp named MAGIKARP
If a team has less than six pokemon, the empty slots will still be occupied with data, with a species value of FF. There is another byte, at 284E, that seems to determine the number of E4 victories. I can't test this, though, as changing the byte causes the save file to read as corrupt.
You might also notice that the 256 bytes before the HoF (which I am affectionately calling the "Danger Zone) is filled with FF in a normal new game. I'm not certain if this is changed over the course of the game, as I (obviously) used cheats to beat the E4 early. If anyone knows about this, or has a late game save file that has never encountered a glitch pokemon, feel free to let me know.