Saurik has officially pushed an upstate of Winterboard for iOS 9. According to the notes from Saurik:

Version 0.9.3919 is effectively just the smallest possible update for iOS 9.

As per the change log, this update also:

• Fix Calendar Icons (Surenix)
• Don’t Crash Spotlight Search

It also appears that Saurik only tested through using a popular theme from Surenix – ayecon to fix some of the obvious issues since iOS 9.

Head over to Cydia and refresh the repos and you will be able to receive the update. It will require a respring to take effect.