What happens to the picture of my face and ID after I've been verified?

At Kit, we use a provider use a provider, Jumio, to facilitate this identity check. You can find their privacy notice here 

This document outlines:

• Jumio will retain the personal information for (i) the period necessary to fulfil the purposes
  and (ii) as long as required by law or (iii) as long as relevant potential legal claims are not yet time-barred.
• Jumio will permanently destroy such biometric data derived from images and recordings in
  its possession within three years after you first provided those images or videos.