ICO Converter is a program found online that will take any image file and convert it into an icon. Take a PNG, GIF or JPG and convert into icon files.

The brown box icon appears when a synced file has ‘Files On-Demand’ feature enabled and is yet not downloaded. To fix this, you should disable this feature in OneDrive and see if it works for you.

Apple makes it easy to change icons for files and folders on Mac. Here's how it works, along with tips on using images or changing the folder icon color.