The "ubuntu-wallpapers" package has just been updated in Ubuntu 11.04 Natty Narwhal and it now includes wallpapers from the Ubuntu 11.04 community contest:

Realtime Sunlight Wallpaper is an application which sets your wallpaper to an image of the Earth's sunglight/darkness - updated every 30 minutes. The wallpaper also displays clouds which are updated every 3 hours with the current weather satellite imagery.

There are no "best wallpapers" or "best themes", as it depends on one's taste. But for me, these are the best 3 Ubuntu 10.10 wallpapers so far:

Searching for something totally unrelated, I stumbled upon an amazing theme pack created by Izo called "SHI10 GTK Linux Suite".

Here is an amazing wallpaper you can use to organize your your desktop(s) to increase productivity:

The Ubuntu Wallpapers package in Ubuntu 10.04 Lucid Lynx will be updated in a few minutes with the wallpapers from the community contest.

You can see all the wallpapers (and the Ubuntu 10.04 default wallpaper obviously) in the screenshot below:

Ubuntu 10.04 Lucid Lynx new themes and logo were made public only a couple of days ago but there are already quite a few "goodies" available based on this new artwork.

Yesterday we say a beautiful BURG theme based on the new Radiance theme, but since then many artists have been playing with the new wallpaper, logo, etc. Read on!

Dichotomy GTK theme

Epidermis theme manager is an open source GTK application for managing, automatically downloading and installing themes of various types, in order to transform the look of your Ubuntu desktop, from the moment you turn it on until the moment you turn it off.

Gnome-look.org has a LOT of wallpapers but to download all of them them, you need to do a lot of clicking. Here is how to download them all with a single command

We wrote about different automatic wallpaper changer applications either for Windows, Linux and / or Mac OSX but Wally is special. Wally is a Qt4 wallpaper changer, using multiple sources like files, folders, FTP remote folders, Flickr, Yahoo!, Panoramio, Pikeo, Ipernity, Photobucket, Buzznet, Picasa and Smugmug images.

Gnome-Art Next Generation is the successor of Gnome-Art and lets you change your Gnome-themes (icon-, wallpaper-, splash-,...-themes) with one click. It is in an early stage and under development but it looks very promising already.