I believe there's no real yes or no answer to this question. Calling someones art a decoration sounds pretty degrading to me, but to be honest some drawings and paintings are total trash. Personal taste and perception determines what one might call art. A painting may elicit strong emotion to someone and another viewer could feel totally apathetic. If Jackson Pollock can splatter paint on a canvas and have those paintings be worth millions of dollars then how can we set limits to what is art and what is not. In conclusion there is no way to differentiate a piece of art and a decoration.