I'm assuming that 輝やいて is a typo for 輝いて. (Maybe it's a variant spelling, I don't know).
This て is simply 'and'. So 置かれて輝やいていた is nothing more mysterious than "was set and was shining".
You ask about whether one action modifies the other. Many times a clause in て-form can adverbially modify the following clause, e.g.
Could be "he sat on the wall and ate" or if you treat the first clause as adverbial it would be "sitting on the wall, he ate". But I feel it would be a bit of a stretch to claim this was the case with your example sentence.
The bit that puzzles me is 比いない, which I'm assuming means "without equal".
So altogether we have:
That matchless white body was placed in front of a twilight background and was shining.
Weird sentence. What's the context?