The official jQuery UI theming module is great to get a custom CSS and see all the icons available with the jQuery UI CSS framework. There is over 100 icons available and could be hard to get their class name.

On the official website you need to put your mouse over the icons, to be able to view the name to be used to display that icon.

We have created a tool (that could be improved in the future) that displays all the icons, and you just need to click on the chosen one to have its name displayed bellow inside a input box. So that you can just copy paste it.

Here is the link: http://yougapi.com/freebies/jqueryui-icons/