Linux Debian major release 9 (codename “Stretch”) will be released “when ready”, but maybe almost in may 2017. But it actually has its own style already, for Wallpaper, Colours, Grub bootup and others.
These are some Mockups/Previews:
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Source (read more): Bits from Debian – “softWaves” will be the default theme for Debian 9
Wiki Debian : https://wiki.debian.org/DebianArt/Themes/softWaves