Things you need to have:
1. Jailbroken iphone
2. Download and install Foldericons v. 2.07 in your iPhone (Don´t open it in your settings)
3. Download and install iFile in your iPhone
4. Download and install DiskAid or iExplorer in your Mac OSX
Process:
As soon as you already have installed everything open your DiskAid and put the icons you want for your folders in the following path:
Root/Private/var/mobile/Media/FolderIcons
Then open in your iPhone iFile and look for the following path:
/var/mobile/Library/Preferences/pl.vertex.foldericons.plist
Now, DELETE the pl. vertex.foldericons.plist and SAVE.
Now go to your iPhone Settings and look for the Cydia App FolderIcons
Enter to the FolderIcons App and click over the Enable button and DISABLE Foldericons.
As soon as it is DISABLE now you can begin choosing your icons for all the folders you want to change and Enable or Disable, Badge, and Mirror Image, etc.
When you finish doing these, Enable the Foldericons Button and that`s it.
If you want to change an icon afterwards REMEMBER to First DISABLE Foldericons button and then do the chantings.
Now your iPhone won´t crash anymore.