There have been many suggestions for various attributes, and most of them will never be implemented. It would not be useful for there to be a list of dozens or even hundreds of attributes. They're effective because they're limited to a small number of the most essential attributes people will likely find the most useful. Attributes that would apply onto only a tiny fraction of boxes (e.g. an icon for boxes that require a GPS device) or attributes that would apply almost universally to all boxes (e.g. an icon for boxes that already include a writing utensil) aren't particularly helpful and therefore have almost no chance of being used.

And finally, attributes are also intended to help people pick out the boxes that would most suit their purposes, so those that help people separate boxes they're interested in from those they are not have a better case for being added. For instance, one popular suggestion is a bathroom attribute so people can know if there are restrooms nearby. Besides the fact that restrooms are often only open for limited hours or limited times of the year, it's unlikely that anyone will use that as a decision for whether they will look for the box or not. (They might use it to help decide if they should go to the bathroom before looking for the box, but it's very unlikely anyone would avoid looking for a box simply because no restrooms are known to be nearby.)