Bookmarks function much the same as Services, in how groups and lists work. They're just much simpler, smaller, and contain no extra features other than being a link out.
The design of homepage expects
abbr to be 2 letters, but is not otherwise forced.
You can also use an icon for bookmarks similar to the options for service icons. If both icon and abbreviation are supplied, the icon takes precedence.
By default, the description will use the hostname of the link, but you can override it with a custom description.