Folder icons : Images used as icons contracted or not showing

Hi everybody,

After upgrading to High Sierra on my MacBook Pro, I have problems with folder icon that I used to make on Sierra very easily by dragging an image and dropping onto folder icon when Get info window is opened. Now the image is somewhat contracted if shown at all. Sometimes I just get the general icon for .jpeg or .png file. On Sierra, everything was fine, the image kept its ratio and the icon was the same as the image. That's what I loved. Does anyone else have this issue or knows something about it?

Thank you!