I have a few entries if the contest is still open.
I used the official disco dingo mascot that the Ubuntu Twitter account posted.
Here is my adaptation for the default wallpaper;
There are other variations of the disco dingo wallpaper I have done based on 80s art style using Gravit Designer that can be viewed on my twitter. I decided to post a link to my twitter to avoid potentially choking this thread with the images.
Let me know what you guys think.