I'm installing an ipa manually to /private/var/mobile/Applications/uuid/my app. The only problem for me is the app icon is blank? Does any body have any idea how I can solve the problem?

Thanks

Did you added a icon to it in the app package?
A note: Unix comandline /hello world is actually /hello\ world.
Also the best way to create a app (without Xcode) is to get a existing app from Cydia, SSH it to Putty/Terminal or mount it on your PC/Mac/Linux Desktop, delete the script and modify the other images, create your own script, change app name and put it into your iWhatever.

Did the best to help and welcome to iPad forums and hope you will/have enjoyed your iPad.

Yes, there is an icon in my app folder. (And I tested by installing through Xcode, the icon was shown correctly).

Actually the reason I want to install it manually is that I'm going to create an app like installous.

By the way, I tried the installBash.sh in installous, the icon is also blank after installation.

Sorry can't help you about your other problem. I never jailbroken my iPad and I know only a little about any programming. I only know these stuff because I've got a book called "iPhone Hacks" which is great but outdated. I did my best to help you.