This is what happens if you let criminals choose the sentence
It really depends on the country. France and Belgium, as you wrote. Germany, they expect a tip and look at you angry if you don’t. Italy, they add a service charge at the end that is nowhete advertised. Turkey, they invent a random price at the end, complaints only taken if you’re local. (I’m slightly exaggerating)
Install the package kdegraphics-thumbnailers, and then depending on the file manager you may have to enable previews, e.g. in Dolphin > Configure Dolphin > Interface > Previews.