guys I created the Named_Logos folder in thumbnails/Nintendo - Game Boy I inserted the png file but once inside retroarch I always see the cartridge logo and not the custom logo… what am I doing wrong??
Did you put in User Interface > Appearance > Playlist Icons = “Content Logo”?. Also make sure that the pngs are named exactly as the entry in the games.
That might change slightly. There’s a possibility to just support Named_Logos directly in RA and the RA thumbnail repository, like all the other artwork. See this PR.
You need to replace the following characters in filenames with a _ according to the docs here.
&*/:`<>?\|"
in user interface/appearance I don’t have playlist icons but icon theme, primary thumbnail and secondary thumbnail
That means that you don’t have installed the updated version. Download the latest branch of Retroarch.
Ok thanks 
I didn’t understand that nightly was needed! now everything is ok… I put the cartridges instead of the logos and it’s very nice… but when I pass over the titles the icon enlarges and covers some things… is there a way to not enlarge the logos when I pass over them?