In the right corner of any list in Financials you will find icons that let you switch view on the list. A list can be viewed as a detailed list, which is the standard view. But you can also switch to view as tiles, which will show less detail on the specific record and stack the entries as tiles. This view is very useful to gain an overview of several entries and is in particular useful on smaller devices, because it makes each entry easier to tap.
On the Items list, having pictures helps you get a quick overview of what you sell and switching to the tiles gives you an item catalogue to browse through. If a picture is defined for the specific item, you have a third option besides the detailed list and the tiles; the large tiles view. This view displays large pictures for each entry.
You can import a picture for a specific item by going to the Item card and to the right select Picture and then choose Import. Likewise you can export a picture to a file or delete the picture for the item.