From what I can tell it determines the unit.bin image used by characters using the sprite set '82 Monster'.
I had 3 units set to M. Portrait 91 (Minitaurus) & M. Palette 1, but with M. Graphic 11, 13, & 14. (The one set to 12 didn't join for some reason.) Anyway, the one with 11 looked like a byblos/apanda and the other two looked like demons. All with the Minitaurus palette & portrait.
Has anyone experimented with this value to see what happens with higher values?
I have to say... I'd never let the person join after I'd experiment with it. But as far as I was Ever aware, that was just a monster identifier, for instance, F and 10 are Dragon and Hydra, if you set all monsters to have this F or 10 Dragon only abilities work on all of them. As I said, I was only aware of them as Monster ID's so to speak.
Interesting.
So it determines monster type and the graphic used in the formation screen.
OK. I found this out.
M. Palette, as we know, determines the portrait and sprite used by a unit.
M. Palette determines the palette used from the sprite selected by the M. Portrait value.
M. Graphic determines which monster slot from Unit.BIN is used as well as the 'monster type'.
Discovered values for M' Graphic thus far:
1-10 - Chocobo-Hydra
11 - Byblos/Apanda
12 - Serpentarius
13 - Demon
14 - Demon (dup or second type?)
15 - Steel Giant
16 - This loads the spot from Unit.BIN where the text is. If we could move that text we could add another monster graphic/type.
17 and on - <blank>