I kind of talked about it earlier when mentioning how the growth of Blackbeard's beard mirrors his increasing power, but in general I like the evolution of his style over the course of the series.
Back when we first met Blackbeard he was basically an NPC. That's no knock to him, given how Oda goes out of his way to make his NPCs unique and interesting, but there was nothing special about his initial appearance. He’s even a member of the fugly shoe club!
By the time he fights Ace he's got the captain's coat and is rocking a lot more jewelry. The guy's got rings on every finger as well as bracelets to go along with his thicker beard
Now in Impel Down he's added the tricorn hat and fancy necklaces, and--more importantly--is no longer wearing his arms in the sleeves of his jacket. There is no greater indication of authority in the One Piece universe than a man who refuses to wear his arms in the sleeves of his coat.
Post time skip, Blackbeard's fully grown beard makes it impossible to tell if he's still got the necklaces, but to make up for it he's now wearing earrings and has upgraded his hat to one with his jolly roger, adding some spiffy feathers to really zhuzh it up. He's again wearing the sleeves of his captain's coat, but the feather coat...thing...that descends from his hat drapes over his shoulders and mimics that shape, broadening the shoulders of his silhouette and making him appear even larger than he already is
Each change individually doesn't make that much of a difference, but added all together it shows the journey of the nobody biding his time in the background into the ostentatious pirate lord who plans on conquering the world
