Even when set to their largest setting, pcmanfm's thumbnails are small on a FullHD screen and tiny - undiscernable / ununsable - on a 4K display.
It would be good if pcmanfm allowed you to scale thumbnails big enough so that you can make them out on 4K / 8K+ displays.
Anonymous
Thank you very much for reporting this. Larger sizes (up to 512x512 which is 1/4 of screen height on 4K display) will be added in 1.3.1 release.