Navigate to your PES installation folder (e.g., C:\Program Files (x86)\KONAMI\Pro Evolution Soccer 2017\img ). Here you will see files like:
: Change the background images and button icons within the game's user interface.
PES IMG Explorer is a specialized file management utility designed to open, view, and export files contained within the .img containers used by the Pro Evolution Soccer series (primarily from the PES 2008 to PES 2013 era).