September 2017
Car trunk customization in 2015/16 reboot was either a full carbon option or removing car logos.
There should be another option-trunk venting.
I`ve seen this on some cars such as the silver/orange Speedhunters GT-86,then Rallycross EVO X`s.
Example bellow is Joon Maeng 2007 2JZ BMW Z4.
September 2017
As I said with the window customization, this probably will not happen. It would be cool though.