I agree with the picture hangers. I usually buy something like this. You can find them very cheap in multi packs.

https://www.amazon.com/gp/aw/d/B000OL0U28/ref=mp_s_a_1_6?ie=UTF8&qid=1494362584&sr=8-6&pi=AC_SX236_SY340_FMwebp_QL65&keywords=picture+hangers&dpPl=1&dpID=31nJKniOUjL&ref=plSrch