BN the max height is 2'7", N the max height is 2'11"
Here's a photo coursewalk of a good event in Area V. I'm linking to the novice level photos, but they have two BN slideshows as well. Welcome to Greenwood Farm, Inc. : Novice Course Walk
Ramps are also a good idea. As are stacked logs, large individual logs, you can make a nice oxer out of different logs, a table, it's only limited by your creativity. Just remember, if they're going to be small make sure they're friendly and inviting, as well as encourage a good jump. Ascending builds are going to be best. Also make sure if you paint them to make a clean "ground line" with the colors. I suggest a stripe of light grey or white near the base of the jump if it's going to be painted mostly a dark color or be placed in the shade.
ETA: I'd also include some really tiny jumps, just in case any non-eventers want to have fun or in case people have a young horse they want to introduce to jumping in an open space.