Custom Desktop Icons Have disappeared.

After updating to High Sierra (current 10.13.1), all my custom desktop icons reverted to the plain blue folder icons. I download new custom icons, but when I click on "Get Info" it only shows the standard "Preview" icon -- not the actual image of the custom icon. So, nothing I am doing is returning me to the custom icons and I'm forced to stare at blue folder icons all day. Any suggestions?