I have herd several people using "danke schön" online. "Thank you, beautiful" is not something I would say in english. Do Germans use "Thank you, beautiful" more casually? Is this a normal thing to say? Would it come across the wrong way, or just be nice?
Schön also means "Good", "Well", so it's OK and used by everyone everywhere.
Depends on who you're talking to. If you're talking to a man - "Danke schön, Schöner." If you're talking to a woman - "Danke schön, Schöne."
Well, if you want to make a mirror sort of effect, you could say, "Danke schön, schöner Dank!" (Thanks, nice thanks!) But that doesn't make too much sense...
You will get to know that German often used adjectives in their basic form as adverbs. This is such an occasion. "danke" is the first person singular of "danken" = "to give thanks"/"to thank". "danke schön" therefore means literally: "(I) thank (you) nicely." It is very normal to say. An answer could be: "Bitte schön." =(lit.) "(I) please (you) nicely." = "Here you are."
I hope I could be of help.