• Title page design
• Logo design
• Creating icons
• Website design and implementation
• Miscellaneous artwork for wiki and social media sites
• User Interface and usability design for applications like Quickshot
• Style definitions

If you want to help out, the best thing to do is to email our mailing list or join our IRC channel and tell us what your skills are and what you would like to do.

Mailing List: ubuntu-manual@lists.launchpad.net

To have a look at the artwork specification, mission statement, target audience and design guidelines, have a look at the Artwork page.