Books that did not win contests can be added to collections at the owner's discretion. I don't remember who (@Jeremy Thomas ?) said that Inkshares sends an email to collection owners periodically with books they might consider for their collections.
@Jim McDoniel 's book has added to the Sword & Laser collection after the contest. If Jim stops in maybe he can give some insight on what the process was like.
If you check each collection there is a pitch option. So you can send any of your books to a collection for consideration at any time. Thought, each collection owner might have their own rules for what they are taking or when they are willing to receive it.
A children’s book for adults (who occasionally behave like kids). The one book about politics that won’t destroy your family and friendships if you read it together. (It might even save them.)