So, I've finally updated the functionality of IOI Database and now there is IOI 2013 with a status of future olympiad. So, no results and tasks. Also participations in future olympiads doesn't count to country statistics and hall of fame, until the olympiad is concluded. So, the list of IOI 2013 contestants is available here. It already includes all the contestants I've seen in CF threads with the exception of Czech Republic due to the submitter not knowing the team for sure. I will update the contestants from all 4 threads on CF (I would like to say 3, but someone will post the team here, even if I ask to not post any teams in this thread to keep this information on CF spreading to minimal amount of places. I'm asking now, by the way), but you can also add teams or edit handles (like TopCoder ones) directly in the database.
I would also like to note that the contestants table is also available for every past olympiad. And yes, it's still not full in some years.
tl;dr: IOI 2013 Contestants