Volume 25 Bonus Chapter (and Extra Illustrations) : r/OnePunchMan

Volume 3, Undead Unluck Wiki

Volume 25 full look. : r/OnePunchMan

One Piece 1080 Tcbscans

All illustrations and bonus content from volume 26 : r/OnePunchMan

Volume 25 illustrations [HQ] : r/OnePunchMan

Chapter 31, One-Punch Man Wiki

One-Punch Man, Chapter 174 - One-Punch Man Manga Online

Changes and Redraws in Volume 24; compared to the online releases. There were only 4 since the chapters were already redrawn, description of the changes is under the images. : r/OnePunchMan

Vol 24 extras (The rest in Vib's post) : r/OnePunchMan

The Volume 28 bonus chapter is about Watchdog Man! : r/OnePunchMan

All illustrations and bonus content from volume 26 : r/OnePunchMan

The Volume 28 bonus chapter is about Watchdog Man! : r/OnePunchMan

Volume 23 Illustrations [HQ] : r/OnePunchMan

Inside Cover and Back Cover,Bonus Chapter and Extra Illustrations from Volume 26 (Scan/HQ) : r/OnePunchMan

Some extras from volume 26 (Low quality) : r/OnePunchMan