There are 7 named categories of stamps.
Select a set of stamps by name from the drop-down list to the left of the Stamp samples.
Use the arrows at the right of the Stamp box to scroll through the stamps within a set, or click the drop-down arrow to view the stamps gallery.
When you see the desired stamp, click it. It will be highlighted with a different shade of blue and it will be shown in the sample box at the current Size and Angle.