Edit: Thanks to Aazealh for the list!
Volume 22: Guts and Casca / Guts and Griffith
Volume 23: Griffith and his apostles / Guts and Casca walking in a dreary plain
Volume 24: Schierke and Ivalera / Isidro training against sticks
Volume 25: Flora and Schierke / Troll
Volume 26: Helmet of the Berserk's armor / Serpico and Schierke buying apples
Volume 27: Composite shot of the Pishacha army / Schierke teaching Farnese, making leaves levitate
Volume 28: The moonlight boy / Guts' group walking uphill towards the horizon
Volume 29: Farnese in a ball dress / Ivalera and Puck dressed in sea shells
Volume 30: The Daka riding tigers / Serpico
Volume 31: Daiba / Guts & Schierke (in astral form)
Volume 32: Griffith on his horse / Ganishka in armor
Volume 33: Ganishka's final form / Roderick
Volume 34: Close up of Guts' face while wearing the armor / Irvine and Sonia
Volume 35: Isma / The ghost ship
Volume 36: Guts in the armor / Isidro, Isma, Schierke and the elves
Volume 37: Young Guts / Erica and Rickert
Volume 22: Guts and Casca / Guts and Griffith
Volume 23: Griffith and his apostles / Guts and Casca walking in a dreary plain
Volume 24: Schierke and Ivalera / Isidro training against sticks
Volume 25: Flora and Schierke / Troll
Volume 26: Helmet of the Berserk's armor / Serpico and Schierke buying apples
Volume 27: Composite shot of the Pishacha army / Schierke teaching Farnese, making leaves levitate
Volume 28: The moonlight boy / Guts' group walking uphill towards the horizon
Volume 29: Farnese in a ball dress / Ivalera and Puck dressed in sea shells
Volume 30: The Daka riding tigers / Serpico
Volume 31: Daiba / Guts & Schierke (in astral form)
Volume 32: Griffith on his horse / Ganishka in armor
Volume 33: Ganishka's final form / Roderick
Volume 34: Close up of Guts' face while wearing the armor / Irvine and Sonia
Volume 35: Isma / The ghost ship
Volume 36: Guts in the armor / Isidro, Isma, Schierke and the elves
Volume 37: Young Guts / Erica and Rickert