Ubuntu – download Xubuntu released wallpapers

I doubt it has started yet. 14.10's contest started in August. This is what Iain Farrell had to say:

1. Images shouldn’t be too busy and filled with too many shapes and colours, a similar tone throughout is a good rule of thumb.
2. A single point of focus, a single area that draws the eye into the image, can also help you avoid something too cluttered.
3. The left and top edges are home to Ubuntu’s Launcher and Panel so be careful to consider how your images look in place so as not to clash with the user interface. Try them out on your own desktop, see how they feel.
4. Try your image at different aspect ratios to make sure something important isn’t cropped out on smaller/ larger screens at different resolutions.
5. Take a look at the wallpapers guidance on the Ubuntu Wiki regarding the size of images. Our target resolution is 2560 x 1600.
6. Break all the rules except the resolution one! :D

Looking at this OMG! Ubuntu! article, submissions are apparently made to a Flickr pool.

For Ubuntu 16.10 (Yakkety Yak), the contest is already open for submissions and will close on 26 September 2016. Submit your wallpaper at https://www.flickr.com/groups/ubuntu-fcs-1610/. Read more about the guidelines at https://wiki.ubuntu.com/UbuntuFreeCultureShowcase, which I will copy and paste here for your convenience:

Wallpaper

We're looking for photographic wallpapers: lovely backgrounds that greet the user on Ubuntu's welcome screen and at login, and provide a main color for the Unity Dash! We're also looking for an illustrative wallpaper that plays off the theme of the current development release (for 16.10, that's Yakkety Yak [1]).

• Images shouldn’t be too busy and filled with too many shapes and colors, a similar tone throughout is a good rule of thumb.

• A single point of focus, a single area that draws the eye into the image, can also help you avoid something too cluttered.

• The left and top edges are home to Ubuntu’s Launcher and Panel so be careful to consider how your images look in place so as not to clash with the user interface.

• Try them out on your own desktop; see how they feel. Try your image at different aspect ratios to make sure something important isn’t cropped out on smaller/ larger screens at different resolutions.

• Take a look at the wallpapers guidance on the Ubuntu Wiki regarding the size of images. Our target resolution is 3840 x 2400. This might result in a centered, 1080x1920 cropped image on Ubuntu phones, so keep this in mind!

• Break all the rules except the resolution one! :)

[1]: I have changed "for 16.04, that's Xenial Xerus" in the wiki to "for 16.10, that's Yakkety Yak".