To use different icons for your pictorial chart categories:
❶ Select the chart (one click) and expand the Chart properties tab in the right sidebar
❷ Expand the Icons tab.
There you'll be able to change icons for each of your data categories (rows from your data table).
In the free version of Infogram only a limited amount of icons are available, however with a paid subscription you will get access to a huge, 20K+ icon library!
If you want to use different icons for each tab in your chart, see here.