Etchings and credit

Here's the piece I finished last night, entitled "Beauty on Trial". It's now the the third piece I have done with some of the etchings from the 19th Century "The Art Journal" (refer to my last post) as my "base" element. I love these etchings and I REALLY enjoy working on collages which enhance (?) the etchings. But here's the conundrum... I'm not at all worried about copyright considerations by using these etchings elements; what I am feeling a little strangely about (and I don't usually have this feeling) is how much "credit" I can take for the inherent beauty in these pieces. The etchings give me a distinct "advantage"; a "head start", if you will, when it comes to the aesthetic appeal of these compositions. I rarely worry about this with other collages I have done. Perhaps I just appreciate so much the technical quality of the etchings. Of course, it will not stop me from doing more collages in this "series'. I am SO happy to be "re-purposing" these images into my collages and letting some of the world see them again after 140 years!