User:Jmabel added a new proposal on December 1st, which has gotten some support. Unfortunately, it's too late for more proposals to be added. We began the survey with a two-week phase where people were invited to submit proposals, and each proposal needed to be endorsed by another user in order to move to the voting phase. That was Nov 9th to 22nd. This is the second phase, where people are invited to vote on the proposals that were submitted. You can read more about the whole process at Community Tech/Community Wishlist Survey description.
I've archived the proposal and support votes below. Let me know if you have questions. -- DannyH (WMF) (talk) 18:30, 7 December 2015 (UTC)
Along with other search terms, be able to confine search to an intersection of categories, or not in a particular category. Also, in these and other cases, be able to specify with up to n levels of child category. E.g. search for Adirondack chair, but not in Category:Adirondack chairs; search for "Cedar River", but not in Category:Mount Rainier or any of its up-to-fourth-level children; search for intersection of Category:52nd Street (Manhattan) and Category:Black and white photographs. (I'd be glad to see this lumped with other related ideas.) - Jmabel (talk) 17:14, 1 December 2015 (UTC)
Support This can be very useful, though a weak point is that too many pictures are not properly categorized. E. g. some people might think that if they search for intersection of Category:52nd Street (Manhattan) and Category:Black and white photographs, they will receive all black and white photographs of 52nd Street in Manhattan available on Commons, which will not always be true. Jan.Kamenicek (talk) 18:36, 1 December 2015 (UTC)
Jan, part of the goal is to be better able to find images that haven't been appropriately categorized. For example, if I looked for images that are in Category:52nd Street (Manhattan) but not in Category:Black and white photographs, I could eyeball for B&W and spot some that perhaps should be added to the latter. - Jmabel (talk) 00:09, 2 December 2015 (UTC)
Support - I frequently work in Commons to populate categories that are under represented. Usually I want to see items containing description "X" which aren't members of "Category:X" or its subcategories.SBaker43 (talk) 03:26, 7 December 2015 (UTC)