Green wall art, by which green you actually mean.

The four greens people mean

• Sage — grey-green, low saturation. The safe one. It reads as a neutral in most rooms and sits with warm timber and off-white without argument. More on sage specifically.
• Eucalypt — sage with more blue in it. Cooler, and better in a room with grey or white rather than cream.
• Olive — yellow-green, warm and earthy. Belongs with terracotta, tan leather and rattan rather than with cool greys.
• Forest — deep and saturated. Not a neutral. One piece will hold a wall on its own and fight anything else strong you put near it.

How much green is too much

If the room already has plants, a green sofa or a green splashback, artwork in the same green makes the whole thing read as a theme rather than a scheme. The usual fix is to move one step: if the room is sage, go olive or forest in the art. The relationship still reads, and nothing looks matched.

In a room with no green at all, art is a good place to introduce it, because it is the one element you can change in five minutes if you tire of it.

What green sits with

Warm greens (olive, moss) with terracotta, ochre, tan, unfinished timber and cream. Cool greens (sage, eucalypt, forest) with grey, white, black, and brass. The mistake is mixing a warm green with cool greys, which makes the green look dirty rather than earthy.