Here's how I fixed the "Suave HD" theme in Cydia, built for for iOS 4.2.1, work on iOS 6.1:
- Go to /Library/Themes/Suave HD V4.2.1 (theme)/Bundles/com.apple.camera and rename
Icon@2x.pngtoCamera@2x.png - Go to /Library/Themes/Suave HD V4.2.1 (theme)/Bundles/com.apple.mobileipod and rename
icon-MediaPlayer@2x.pngtoicon@2x.png - Go to /Library/Themes/Suave HD V4.2.1 (theme)/Bundles/com.apple.mobilemail and rename
icon@2x.pngtoIcon@2x.png - Go to /Library/Themes/Suave HD V4.2.1 (theme)/Bundles/com.apple.mobileslideshow and rename
icon@2x.pngtoPhotos@2x.png - Go to /Library/Themes/Suave HD V4.2.1 (theme)/Bundles and rename
com.apple.youtubetocom.google.ios.youtube - Go to /Library/Themes/Suave HD V4.2.1 (theme)/Bundles/com.google.ios.youtube and rename
icon@2x.pngtoIcon@2x.png - On iPhone 5, the wallpaper obviously won't fit the screen so you just have to live without it - delete /Library/Themes/Suave HD V4.2.1 (theme)/Wallpaper.png
- Open WinterBoard, toggle anything on and off to show the Respring button and tap it.
Obviously there aren't icons for new apps such as Reminders, Passbook, Newsstand, etc. so you'll just have to hide them or stick them in a folder.
Suave actually has updated versions available at http://macthemes.net/forum/viewtopic.php?id=16804800. They contain way more icons than the iOS 4.2.1 package in Cydia and obviously don't require any renaming :)