I was wondering if it would be possible for artists or graphics designers to paint an almost identical copy of an existing photo? I ask because I have a grainy photo and it would be nice to see it large. Does such a technique exist?
It's possible to make a copy and may not even require any artistic skill or experience as a painter. It may just depend on your hardware.
In the movie, Tim's Vermeer (see: trailer on Youtube), Tim Jenison is obsessed with Vermeer, and whether or not he used optical devices to aid in the photorealism of his paintings. He eventually attempts to recreate a Vermeer painting by using an optical device of a small mirror canted at 45° to the scene he wants to paint (a camera obscura is no good because it's hard to paint sitting in the dark, and you can't judge color properly when color is projected on top of what you're painting). The image in the mirror guides him to line placement and color on the canvas. One of his test trials is to recreate a black and white photograph using only black and white paint, and he accomplishes it.
This Youtube video was made by someone inspired by the film to attempt the same feat on his own. So, yes, it's entirely possible, even by someone unskilled with a paintbrush. It may not be artistic or interpretive, but the results are certainly recognizable as a replica of the photograph.