Per Apple's requirements, iPhone non-retina appicons should be 57x57, retina should be 114x114, and iPad should be 72x72. The current Info.plist template supports appicon.png and email@example.com, but nothing for ipad. Please add suport an appicon72.png so that a universal app can include icons for all three target devices.
A fix involves a simple update to the /Library/Application Support/Titanium/mobilesdk/osx/VERSION/iphone/Info.plist file. See the following Q&A for the inspiration for this fix: http://developer.appcelerator.com/question/118232/universal-app-submission-error#answer-214335