I have a work folder under my Home folder that I store all of my work-related documents. I wanted to put my work’s logo on the folder to make it stand out.
I found a great thread with some tips. Basically, I downloaded a graphic from the company website with the logo on it. I used Gimp to crop and resize it. Then, I saved it to the folder: $HOME/.icons/hicolor/48×48/emblems (I had to create the .icons directory). Finally, when I right clicked on the folder and viewed the property, my new icon was in the list of emblems.