Data-miners have been finding new files that have been added to the recent v6.2 patch and it looks like new files have been added to award players that reach level 100. There were no rewards that were given previously, but leaks suggest that this could change. Data-miner @HYPEX has found three rewards for players that reach level 100. There are files for a spray, emoticon and banner.
Level 100 Rewards
It has not yet been confirmed by Epic if these awards will be given to players that reach level 100 in this season or in future season, but we will keep you updated with the latest.