Getting your logo, or other branding, as high as possible on your stand, is probably the single most effective design feature you can use.
This will get you noticed over the heads of others, within a crowded venue. Making you easier to locate and giving you a stronger presence in the hall.
Be aware that most venues, such as Olympia, the NEC and the ExCeL Centre, have a maximum height for an event structure of 6 metres.