Are pictures placed in a Sukkah considered Noiy Sukkah and Muktzah on Shabbos/Yom Tov?
Pictures are considered “Noy Sukkah” and hence should not initially be removed from the Sukkah unless one stipulated beforehand, as explained above. Nevertheless, in light of the above custom to move the items even without stipulation, one may in a time of need move the pictures from the Sukkah even if a stipulation was not made. Accordingly, the pictures are not considered Muktzah on Shabbos and Yom Tov and may be replaced if they fell [although seemingly it is best to do so using a Shinuiy if a stipulation was not explicitly made[1]].
[1] Tzaruch Iyun if in truth they are Muktzah even if a Tnaiy was not made, and is required, as their entire purpose is decorations, and is hence not similar to the Muktzah status of decoration fruits which are in general designated for eating. The practical ramification would be regarding if one may move it to another area of the Sukkah on Shabbos/Yom Tov or tilt it back into position.