This hoverboard doesn't have any unlockable upgrades.
Mosaic is a limited hoverboard released with Subway Surfers World Tour: Barcelona. Like any other hoverboard, it protects you from crashing for 30 seconds. When crashed, it will explode and recharge for a few seconds before it can be used again. It has the appearance of an old jewelry circle. Like most of others limited hoverboards, it costs 50,000.