I think the plural Xs_removed
plus the singular single_X
to refer to a picture with a pair of footwear, where one isn't being worn, is a good way to reduce the variants and help searching for one thing or another. 2 other examples:
A single footwear being worn in the picture: just single_X;
A pair of footwear not being worn in the picture: just Xs_removed.
You know what I meant by X and Xs, but tbh I suggest that the specific tags could be aliased to something like footwear_removed (I'm aware of its wiki) and single footwear, since the posts would also be tagged boots, shoes, sandals, high heels and so on anyway. The problem I see other than ambiguity is that members wouldn't be able to make searches like footwear_removed single_footwear boots
though.