[agosnell]

That sounds like what would normally be called a patron in English. See definition 4 here: http://en.wiktionary.org/wiki/patron#English

But I think patron may have connotations of influence over the artist. (I could be wrong on that.)

[soneca]

#4 is quite similar of what I have in mind. But no connotations of influence in theory - in practice, I imagine that was hard to have zero influence on the supported artist.