First, I think most of us are not really sure if the Yellow Axe question should have been locked in the first place. It was a case of human exception handling on the part of a moderator, and when we discussed it on meta, we either expressed uncertainty or approbation for it. It's not really sound precedence for deciding what's on or off topic in my opinion. However, for the sake of discussion, I will posit that it should be closed in deference to authority.
The best reason I can see for it having been closed is that Dan Bron's answer revealed that it probably wasn't an English word, and as such had questionable ties to the English Language. At best, it was the English language context (for lack of a better word) that rendered the question as being remotely anything about English, which was determined to be inadequate Sometimes some people also complain about typos on similar grounds, e.g. the covfefe question. The logic seems to be if it is not in the English Language, then it can not be related to the English Language. At the risk of putting one of my better answers on the chopping block, I feel it is necessary to repeat that this is why I did not try to answer the paraphrase bracket question sooner, because it shows that I feel this logic is somewhat understandable.
In this case however, the answers show that there is English terminology, even if it is relatively little known and dialectical which renders other image-identification questions significantly different in that they have a stronger association with the English. Indeed, it is not in any way unreasonable to assume that something that many English speakers have frequently seen in everyday life for over a century should have its own distinct name. This is a very, very common utensil found in offices, and I remember seeing these items ever since I was a very young child since my mother worked with papers quite often.
As far as single-word-requests go, image-request questions may even be among some of the better questions we receive, because a picture objectively demonstrates what it is we are seeking and the need for it much better than a contextual sentence or a personalized definition: A picture is worth a thousand words, or so they say after-all. Even though Terdon is otherwise a strict adherent of the contextual sentence requirement, he did admit to me that a picture mitigates against the usual necessity of it in a brief debate. This leads to much more definitive, specific and accurate answers that are of the sort we are supposed to prefer. These also have a fairly good chance at revealing some rather interesting lexical items.
Indeed, among one of the personal favorites of the answers I wrote is the answer to the question I exemplified for Terdon, which was Describe the Color of Raw Liver. In it I suggest words I happened to chance by terminology from heraldic tradition, sanguine (blood red) and its close synonym murrey (the color of mulberries). Sadly, it did not satisfy the questioner so much, so he added to his criteria to exclude similar answers but I think it should be of interest to anybody else looking for a relatively precise word for that color.
Similarly, Is There a Word for an Individual Spark in a Firework? produced some interesting evidence in the top voted answer, and scintilla looks like a promising answer, even though the commentator who mentioned it suggests is of the opinion that it is wrong. Granted, in that case, I do not really think the picture alone is adequate to identify just what is meant: (Does the questioner mean the head or the tail of the ignited firework, or the combination of both as the circle suggests together?) but the question seems to have promise.
The only questionable bit I think is if we really should be answering questions regarding concrete nouns, and personally, I think we should be answering questions regarding the entire vocabulary if they are otherwise within scope. While it may seem tempting to suggest otherwise,major lexicographers seem to all admit to the wisdom of addressing these words.
The Oxford English Dictionary for instance decided not to include proper nouns on the grounds that those were more encyclopedic than lexical in nature, and this led to the very glaring Omision of needful words like African. People wrote in to complain, and it was claimed that since this portion of the dictionary was already published it was too late to fix, and it would remain unfixed until the 1933 supplement was released nearly a century later.
Similarly, I think Johnson's Plan for an English Dictionary makes a compelling case that words of all sorts are needful and merit being addressed in the art of English lexicography, and while we are not quite a replacement for a dictionary, I do believe we intend to serve as a sort of supplement to one when it's necessary since word choice and usage is within scope.