Shut She’eilat Shlomo 2:163

Question: We are building a house and want to know what is the law regarding not plastering or painting "an amah by amah" (half-meter by half-meter) in the house, as a remembrance that the main house - our Temple – is still not built, based on the verse "If I forget You, Jerusalem, may my right hand loss its cunning" (see Tehillim 137:5). In which place and at what height should the amah by amah be left, and should it not be painted at all so that one can see the concrete blocks or can the whitewash or color just not be added or removed?
Insofar as I am a former resident of Yamit (a town in the Sinai Desert which was destroyed when the Sinai was returned to Egypt), it is possible to hang a picture of Yamit inside the "amah by amah" as a remembrance of the destruction?
Answer: The Shulchan Aruch says (Orach Chaim 460:1): "When the Temple was destroyed, the Sages of that generation established that we should never build a plastered and molded building like a building of the kings; rather one should plaster his house with clay and with plaster and leave an un-plastered spot of an amah by amah facing the door" (Shulchan Aruch Orach Chaim 460:1). The halachic authorities are surprised why people do not follow this practice, and they defend people's action in various ways. For example, in the past, their houses were extremely beautiful and there was therefore a need for the amah by amah, but in our times, the houses are simple and there is no need. And there are those who are lenient when building a house in order to sell it (Shut Igrot Moshe, Orach Chaim 1:11), but there are those who reject this idea (Shut Mishneh Halachot 5:71). The Mishnah Berurah however rejects all of these explanations and rules that we are obligated to fulfill the law (Mishnah Berurah ibid. #2). There is no requirement however to remove the plaster or the clay down to the concrete blocks, and it is sufficient to remove the plaster, the paint or the wallpaper. It is possible to leave the clay, since it is somewhat white and gray and certainly not similar to plaster or paint, and it is a recognizable remembrance of the destruction. The essence is that the amah by amah is recognizable.
The remnant should be across from the door, at the height that when a person enters he will see it (ibid. #3). It is not sufficient, however, to hang a picture of destruction. While there are those who are lenient regarding painting a black square, and the Mishnah Berurah even rules that we should not protest against one who does this (Sha’ar Ha-Tzion #8), there are those who prohibit it because they hold that it is like a picture and one should not hang a picture, which is a beautiful object. This even applies if one writes "a remembrance of the destruction" within it (Chayei Adam 137:1) or if the picture's contents are sad (Mishnah Berurah ibid.). And the Levush (chapter 560) similarly wrote that one does not fulfill his obligation with an image of the Western Wall. One therefore certainly does not fulfill his obligation with a picture of Yamit. While the destruction of Yamit is truly a tragedy, one should not compare it to the destruction of the Temple, the source of all of our distress and persecutions. In contrast, the destruction of Yamit is only a minor and passing eclipse in the midst of the rising sun of Zion in all its strength, and this broken piece of Yamit will also be healed speedily.