Simply what you have to do is Join the Theme-Junkie Affiliate Program.Create a new account there and than log in to your account, copy the Theme-Junkie Affiliate code and than paste it in your site.
How Much you can Earn Per Sale?
Whenever you sell a Theme with your Affiliate ID Theme-Junkie will pay you 25% Commission. I think this is one of the best Affiliate Program by only selling the WordPress Themes.
If you need a Theme-Junkie Affiliate promotion Banner than Click Here to get them.
One more thing On Secret Hunt WordPress Theme is also designed by Theme-Junkie.