A nail over even a short period of time with the weight of the frame and artwork together will most likely roll the nail out of the wall. Depending on size two hooks should be used. In cases of very heavy frames the use of wire is not recommended. This is not a hard and fast rule, however, and consideration must be given to individual needs. Paperborne art is not recommended to be hung in high humidity location such as bathrooms.
Direct sunlight is also to be avoided due to heat and ultraviolet light exposure considerations.
Although over fireplaces is a popular place to hang art, consideration must be given to the factors of heat and soot possibly contaminating or damaging the artwork. Consult your framer in these cases. He or she may be able to recommend solutions to these problems. This is the same as a poster. It is signed and numbered and usually printed high quality paper.