I recommend downloading "AppInfo" from Cydia. You can use this to easily check all the apps you have installed the names of bundles folder, eg. 'com.chillingo.cuttherope'. Also often they give the name of what the icon file should be named eg. "Icon@2x.png" or "icon@2x.png" etc.
Sometimes it says the icon file name is unknown, but if you have iFile installed (there is a free version too) you can tap "open in iFile" and it will take you to the application direction and if you just look at the files inside you can normally easily see what the icon file should be named 🙂