Picture frames are considered by many to be more of a necessity than anything. The fact is, a picture frame is going to really complete the perfect picture or painting. It just comes down to finding the right way to complement a look.
Large picture frames in particular are sometimes hard to find with just the right look. The frame needs to be of good quality, especially if the painting or picture just is very valuable. It also needs to be durable, because nobody wants to have to replace a frame every so often.
Finally, color is something that should never be overlooked. Most frames are going to be a pretty neutral color, but taking black over brown or vice versa for certain types of pictures is a huge no-no. That can really mess up a look in a hurry.