iOS Icon/Image guide line

http://developer.apple.com/library/ios/#documentation/userexperience/conceptual/mobilehig/IconsImages/IconsImages.html

Description Size for iPhone 5 and iPod touch (5th generation) Size for high-resolution iPhone and iPod touch Size for iPhone and iPod touch Size for high-resolution iPad Size for iPad Guidelines
App icon (required for all apps) 114 x 114 114 x 114 57 x 57 144 x 144 72 x 72 “App Icons”
App icon for the App Store (required for all apps) 1024 x 1024 (recommended) 1024 x 1024 (recommended) 512 x 512 1024 x 1024 (recommended) 512 x 512 “App Icons”
Launch image (required for all apps) 640 x 1136 640 x 960 320 x 480 1536 x 2008 (portrait)

2048 x 1496 (landscape)

 768 x 1004 (portrait)

1024 x 748 (landscape)

 “Launch Images”
Small icon for Spotlight search results and Settings (recommended) 58 x 58 58 x 58 29 x 29 100 x 100 (Spotlight search results)

58 x 58 (Settings)

 50 x 50 (Spotlight search results)

29 x 29 (Settings)

 “Small Icons”
Web clip icon (recommended for web apps and websites) 114 x 114 114 x 114 57 x 57 144 x 144 72 x 72 “Web Clip Icons”
Toolbar and navigation bar icon (optional) Approximately 40 x 40 Approximately 40 x 40 Approximately 20 x 20 Approximately 40 x 40 Approximately 20 x 20 “Icons for Navigation Bars, Toolbars, and Tab Bars”
Tab bar icon (optional) Approximately 60 x 60 Approximately 60 x 60 Approximately 30 x 30 Approximately 60 x 60 Approximately 30 x 30 “Icons for Navigation Bars, Toolbars, and Tab Bars”
Default Newsstand cover icon for the App Store (required for Newsstand apps) At least 1024 pixels on the longest edge At least 1024 pixels on the longest edge At least 512 pixels on the longest edge At least 1024 pixels on the longest edge At least 512 pixels on the longest edge “Newsstand Icons”