Yes, you can count display items as business expenses. Your starter kit can be included as a regular expense since you got it at/near the same time you started your business; start up costs are for costs incurred prior to starting your business. Whatever your kit is mostly comprised, office materials or advertising for instance, is how you would categorize it.
If the display items are strictly for display and not for sale, you can count them as advertising or enter them under "Other expenses" with a Display Items description.