The last lines of Saki's short story, "The Lumber Room," provide the reader with the answer to this question:
...it was just possible, [Nicholas] considered, that the huntsman would escape with his hounds while the wolves feasted on the stricken stag.
Clearly, the tapestry which acts as a fire-screen greatly delights the imagination of the ingenious prankster Nicholas, who steals into the lumber room and finds wonderful things:
First and foremost there was a piece of framed tapestry....
This tapestry which depicts a stag shot at close range by a hunter with his dog, equipped with mere bow and arrow, who in another part of the design appears to be in harm's way as a pack of hungry wolves look on while he stands with a mere two arrows left, greatly intrigues Nicholas. And, after the success of his clever prank of pretending to not recognize his aunt and, thus, be able to leave her in the water tank, the imaginative Nicholas feels more confident of the future, surmising that like the hunter, he, too, may eschew the harm of the predatory aunt, who is symbolized by the wolves, and live to use his arrow-like wit in order to strike his victim down by outwitting her in her strict, and often foolish, pronouncements and unreasonable punishments.
When, in H.H. Munro's (Saki's) short story The Lumber Room, Nicholas initially gains entrance to the titular space, one is lead to believe that the curious boy's most important discovery is a tapestry "evidently meant to be a fire screen," depicting a huntsman and a large, now-dead stag, the latter apparently having very recently been killed with an arrow by the former. The huntsman's two well-trained dogs stand at attention, certain of their role. The young boy is mesmerized by the image. Munro suggests that Nicholas, in his careful viewing of the tapestry, sees four wolves heading toward the huntsman and his freshly-killed deer. Nicholas' imagination takes over, and he begins to speculate on the fate of the huntsman and whether the four wolves are joined by additional wolves, all of whom are certain to feast on the stag and, presumably, on the man and his two, out-numbered dogs.
So, Munro has established that the tapestry is what most captures Nicholas's attention. He then, however, has his protagonist make another discovery, that of a large book with an unassuming, black binding. Opening the book, Nicholas discovers that it is filled with beautiful pictures of many types of birds he has heretofore never encountered: "Nicholas peeped into it, and, behold, it was full of coloured pictures of birds. And such birds!." The reader can now assume that the book will supplant the tapestry as the more important of the boy's discovery. The reader, however, would be wrong. As The Lumber Room approaches its ending, Nicholas, having exacted his revenge on his aunt by ignoring her pleas for assistance after she has fallen into a large water tank, proceeds to observe the dissatisfaction with which his cousins and brother experienced their trip to the beach, while his aunt angrily but silently endures the triumph of her arch-rival. As Munro's narrator describes the scene:
"The aunt maintained the frozen muteness of one who has suffered undignified and unmerited detention in a rain-water tank for thirty-five minutes. As for Nicholas, he, too, was silent, in the absorption of one who has much to think about; it was just possible, he considered, that the huntsman would escape with his hounds while the wolves feasted on the stricken stag."
With this passage, it is obvious that the tapestry, and the effect it has on Nicholas's imagination, is, in fact, the most significant discovery the precocious child makes upon entering the forbidden lumber room.