As of now, the only reward to getting higher levels is getting access to new jobs. That and getting to level 100 and getting prestige. I think it'd be really cool if there'd be more of a reward for gaining levels, especially the ones after level 50 when you unlock the last few jobs. Rewards like gaining more health when you spawn, or spawning with armor or defense to weapons. It wouldn't have to be anything crazy, just little numbers that add up over time. Something like getting milestones, like every 2 or 5 levels you get one or two extra health / armor when you spawn.