The Avengers custom figures are all by Chris Land.
USAgent is a repainted Marvel vs Capcom Capt. America.
Quasar is a repainted Kull figure with a Iolus head, a cape from capture net Superman and his quantum bands are from an Adam Warlock.
Sersi is a repainted Marvel vs Capcom Moriganna. Her hair is from a Aurora and her belt is a cut band from White Queen's staff accessory.
Zemo was made from a Famous Couples Cyclops body w/ a Spiderman head. His gun was from a lost and space figure, a piece of tube and a gumball machine capsule. As you may have noticed, I did a little redesigning to his suit. (Note: I used an old Marvel trading card as reference, hence the gun.)
Hank is a repainted SMOS Lex Luthor body. His arms are from a Archangel 3 and his head is from a X-Men vs Streetfighter Magneto.
The Black Knight was a repainted Dreadknight body with some sanding. The cape is also from Dreadknight. His head is from a Backlash and his sword is from a movie Blade figure.