I'm not quite sure if this fits in with what you're thinking here, but what I would love to see is a way of categorising icons. A lot of people will already try to organise their keywords by starting them off with the name of the fandom the icon is from, or the kind of emotion displayed in the case of rp icons. If part of this could allow specifying groups of icons under user-set categories, that would be seriously awesome.

I do also really like the idea of being able to see old keywords! I'm always having to take screenshots of my icons before I start switching them up, just in case I want to use that keyword later.