We prepared two new firms that you can start with when you want to complete some exercises.
The Empty Firm has no accounts at all, but has some basic configuration for the statements and the positions of accounts. You can use it if you want to prepare (or import from a spreadsheet) your own Chart of Accounts.
US GAAP Simple Firm has a very basic Chart of Accounts, straight from the Wikipedia page. You can of course edit it as you wish.
Don't forget that you can add accounts on the fly, when you are preparing a journal entry, simply by adding an exclamation mark after their name (you can decide later where to put it in the Chart of Accounts).