@tatsu Looks cool but I think just changing the size makes it pretty hard to tell between the sub tiers. Like if you just see one of them you won't be sure if it's tier 2 or 3 because they both look too similar.
Here's my idea, although I'm not particularly good at the graphics so maybe someone wants to take inspiration from it and come up with their own version, or just use this as a base and make it better. Go for it, you have full permission!
Divisions are differentiated by color, sub-divisions are differentiated by the number of stripes or stars and the final tier gets its own special icon. I tried to go for the commander mask, but it could be anything so long as it strikes fear into the hearts of your enemies.
I guess you need to be careful with colors because of colorblindness, so maybe the border should get progressively more fancy as you go up divisions. Something like
Bronze -> no border
Silver -> Top and bottom
Gold -> Full border plain
Diamond -> Full border embellished
Master -> Even more embellished
Anyway, I've spent too much time making this already
Edit: I worked on polishing it up and heres what I came up with. I kindof made the mistake of assuming the rank numbers increase as you gain rank, but it's supposed to be the opposite. These icons make more sense if subdivision 5 is the top and 1 is the bottom.