Clear signage inside the arena and the navigation there in different transportation modes (driving, public transportation, walking, biking) give a good perception and will make the arrival to your event easier. You do not want anyone to get lost and stressed before a race.
Hand out a map of the arena in an email in prior to the race, or when they arrive. This makes it easier for them to navigate.
Adding nice banners and logos around the arena makes it look like a serious race. It is also an opportunity for you to expose your brand and do some advertising to racers and spectators. Place the signs higher up so they are still visible even if it is very crowded.