As expected, there aren't many differences between the old version and the new one
Canonical is getting closer and closer to the release date for Ubuntu 13.10 (Saucy Salamander) and now they've finally updated the official wallpaper.Canonical usually waits until the last moment to choose the default wallpaper for the next iteration of Ubuntu, in this case 13.10 (Saucy Salamander). The wallpaper was announced a few days ago, but it was uploaded into the official repositories today.
Most of the Ubuntu community doesn't really care about the default wallpaper, but there are a few who criticize Canonical's decision to keep updating the same image over and over again.
This is just the case with the background for Ubuntu 13.10 (Saucy Salamander) and as everyone can see from the screenshot, is hasn't changed much.
Ubuntu 13.10 (Saucy Salamander) is expected to arrive on October 17, along with the other flavors.