Not really an .ICO, but still: Windows also supports BMP bitmap images as icons... Meaning that you can take a bitmap picture, rename it as .ICO, and use it as any other icon.
Of course that way you won't be able to store multiple dimensions inside a single file, but it can be used as an icon...
Of course that way you won't be able to store multiple dimensions inside a single file, but it can be used as an icon...