I was directed here by a debate spawned by a question of mine: Independence of price and wealth in Walras' Law
I'm strongly against the closure of questions centered on pictures. Pictures are an easy way to show, word-by-word, an author's definitions, which are important when dealing with concepts whose formalization differs across textbooks. For instance, whereas the concept "game" is defined only by words in elementary Microeconomic texts such as that of Pindick and Rubinfeld, graduate-level books like Mas-Collel and Whinston's designate game to be a tuple, or ordered set.
An alternative to the use of pictures is the typing of all texts word-by-word which is, more often than not, a tiresome, laborious task, particularly when the use of Latex is required. This would go against what I believe to be one SE's purposes, which is practicity. If one must go great lenghts to solve simple doubts, he or she had better take private classes instead.
Also, I have trouble believing users would truly transcript the author's text word-by-word. In order to save effort, they would rephrase passages, which would confuse other users. After all, if he or she who's asking had a clear understanding of the text, there would be little need in searching for help.
I've used pictures in most of my questions in Math SE, as my history can tell in https://math.stackexchange.com/users/222095/bruno-schiavo, and I've never been flagged for that. In fact, people seem to be pleased by the use of book prints, as it can be seen in (http://mathhelpforum.com/differential-geometry/249557-concept-dx-manfredo.html#post870742).
At last, I don't think question searchability would be greatly compromised by the use of images. Alongside with posting the image, the user must clarify his doubt in the passage and, by doing this, most keywords present in the excerpt should be used. Also, pictures often contain expressions in formal mathemathic language, which has zero search value. There is broad space for inputting keywords for the means of searchability, and this space is the Tag bar, which has, unfortunately, a very poor selection of options. We should focus on improving it.