The composer John Tavener
was a convert to Orthodox Christianity whose art was inspired by Orthodoxy; he eventually branched out in different (religious) directions for inspiration, but said that he remained Orthodox as far as beliefs/affiliation. Alexander Solzhenitsyn
is another possibility, though I wonder to what extent his Orthodox Christianity inspired or informed his fiction and non-fiction. Perhaps a lot, but I haven't read enough of him to know for sure.
Jaroslav Pelikan, while perhaps not what you were looking for, was nonetheless more historian than theologian, so I figured I'd throw him in as someone inspired by Orthodoxy in his "art". I assume philosophers (Swinburne, Hart) and philosopher-theologians (N. Lossky, Berdyaev) are a bit too far off from what you're asking about.
Also, there are quite a few novelists/writers mentioned in this thread
, and this thread