Hi all,
I propose to add an option directly in the Kodi settings to select the maximum resolution of the illustrations (posters, covers, etc.). This would avoid going through the advancedsettings.xml configuration file, which would be more accessible for many users.
This feature will make even more sense with the upcoming arrival of automatic scaling in Kodi (as mentioned in this PR: #25630). This scaling will allow illustrations to be displayed at their actual size before processing by the GPU, thus providing better management of image quality and performance, especially for low-power devices.
Adding this option would allow the user to optimize the use of resources on devices with limited computing capabilities, while avoiding the overconsumption of bandwidth and storage related to downloading very high-resolution illustrations that are not always necessary depending on the hardware.
Or on the contrary, finally enjoy high-definition illustrations ! 
Thank you very much for considering this request,
Bindou