Currently, it would appear that there’s a single contribution, which you can see attached to this article on the right side, so the Debian Project today is making an appeal to the community to submit artwork proposals before the deadline of September 5, 2016. The winner will be announced somewhere around the date of September 26. They are looking for artwork that uses the Debian Logo guidelines, it’s clean, well designed, easy on the eye, compatible with various GNOME applications, and does not require GTK+ or GDM patching. More information can be found on the Debian Wiki, where you can asubmit your artwork. Good luck!