creative ways for clients to "pay" for design

I am interested in how designers and their clients can work in ways other than on a fee basis. E.g.

  • trade fees for equity in a start-up
  • royalties from a revenue generating product
  • trading design expertise for the client’s services or products
  • rewards for successful product launch or navigation of other key milestone, penalty if not
  • payment deferral (e.g. until after a funding round - with some sort of upside)

    Any ideas on what works, what doesn’t etc. welcome - thanks.