Overall there should be hits of orange and black in the interface. White is always nice too.
A) The app icon:
1) Should be a Moodle M with a hat based on the one here: http://moodle.org/mod/forum/discuss.php?d=162906
Here are the specs for icons: http://developer.apple.com/library/ios/#documentation/userexperience/conceptual/mobilehig/IconsImages/IconsImages.html
B) The Dashboard buttons are also icon-sized:
1) Participants: some people / faces, possibly in groups
2) Upload: allows you to send photos/audio/video to Moodle: perhaps an arrow pointing up is enough
3) Web: (might be renamed) allows you access your Moodle site via the web browser
4) Help: (might be renamed) allows you to access Moodle Docs via the web browser
A background image is allowed, if you feel it helps, even a gradient perhaps. Otherwise a flat colour.
C) On the upload page, three more icons would be good, for:
1) Audio recording (soundwave or microphone?)
2) Photo gallery or capture (camera?)
3) Video recording (video camera or movie strip?)
D) On the Audio recording screen it will take up the full screen, we need to show
1) A nice big pretty microphone in the middle
2) 20 images that show recording levels from 0 to 20 (bar graph or dial, whatever you like)
E) On the participants task,
1) on the course listing, an icon for "Course" would be nice. Perhaps based on the one in Moodle.
2) on the user profile, small square icons for Email, Phone and Address would be nice but are not essential
F) On the sync page, we need two small square icons a little like Dropbox does.
1) One showing "file sent".
2) One showing "file not sent yet, still in queue".