While I mostly agree with Troy S. regarding the need to first define the audience and the message for Ubuntu artwork, I have a few ideas for backgrounds I want to try anyway 🙂
After seeing a few Ibex themed backgrounds, I started to think that it might be interesting to concentrate on the horns and to at least hint at a fitting environment. This of course could easily end up looking a bit too hard and agressive for a general audience. Some think that the codename animals should be kept out of artwork. They can be a nice hook to avoid empty randomness and I don’t see how this would do any harm as long as you keep other possibilities open, though.
A concept sketch to define general shapes and colours (those bumps on Ibex horns have to wait):
Full size (1600 x 1200 px)
I took this opportunity to get to know Bazaar/Launchapd: https://code.launchpad.net/~t-w-/ubuntu-artwork/thorwils_backgrounds
In there you can find the GIMP .xcf. It’s in double size and has passe-partout layers for 5:4. 16:9 and 16:10 ratios to check the composition for common resolutions. Please feel invited to use this for paint-overs, colour-tweaks and variations. I might switch to SVG/Inkscape once the concept stands.