Very poor thumbnail quality

Hellow,

I want to make some custom folder icons for my folders like movies, tv, …

On my computer the images are good looking but when I see them as a folder icon on the hub they have a very poor quality.

I tried some icons I found here on the forum (185 x 278, 300dpi, folder.jpg) and the same image but with a ratio of 2:3 but both images looked very poor.

Does anyone know what settings I have to use?

Thanks in advance

There is a known issue with folder icons, as they are not handled the same way as file icons are.  This is a firmware issue.