Blocs comes with five open source icon sets built in allowing you to easily use any of them in your designs.

Changing Icons
When you place an icon Bric into your design or use one of the pre-made Blocs that contains an icon, the icon will already be set. To change any icon in your design simply double click it or if the icon is already active you can also change it by clicking on the preview thumb from the sidebar options. This will open the icon set library window, from here you can search and select the icon you wish to use from any of the 5 sets.