One of the first forged wheels to launch are called Socorro and come in 21 inch size painted in Liquid Blue color with polished lips. The wheels are available in custom fitments for most applications. Pricing has yet to be announced.
Some of those can be seen below with different i8 colors:
While the wheels market might not be as large as the one for the BMW M4 for example, it is still interesting to see if any BMW i8 owners will be adventurous enough to change the looks of their car.
Here is a photo gallery below showing the aftermarket i8 wheels: