Winterboard for iOS7 isnt READY YET.
The file system within iOS7 has been changed from what it was in iOS6. The icon links to the system are not the same anymore therefore you are all getting crashes. Just wait it out, i am sure teams are preparing some solution.
As for some themes working, well its mainly ones which only change the app icons and not the rest of the OS design.
It works, but not fully. It doesn't "support" iOS 7, you can use it, but its bad on RAM, Battery, and is likely to put you in safe mode often
Winterboard was updated by saurik yesterday for iOS 7 and ARM64.