This, first and foremost, was an opportunity to help through your work. The Cause was not the problem, just with the nature of the vehicle of its further expression. IF your image was the best for the purpose THEN by withholding your image you diminish the amount of aid to the end purpose. Who gains by that? Who loses?
Giving is about neither gratitude nor who is giving more. It's not like you are standing against outrageous greed. Your friend deserves the best help possible and it was in your hand. Down the road you can tell your friend that you didn't let them use your image because you didn't like their business model.
FWIW, I hear an awareness of this in your writing; it is bugging you. Perhaps you now understand why. That said, giving, volunteering and donation can neither be required nor its absence be chided. As one who has worked at many ends of non-profit work, I have had to come to terms with this or get resentful, burn-out, and quit. Whatever you decided is right. Life is just not simple.