While event displays could fall into the print category, we put them into the one-off category for a few reasons. The first is that unless your business has a very healthy marketing budget, you will be using the same display for your booth/event many times. Additionally, sometimes displays employ items such as monitors showing a presentation or video, signage, podiums, etc. which fall outside the traditional print category.
With displays, it's important to be aware of issues that affect the effectiveness of your items... the size of the piece(s), where they fit into the space you have, and the amount of information you want convey,
Thinking through these issues beforehand will result in a more efficient means of attracting customers into your booth, as well as informing those who pass by and just glance at your offering.