If you have a backup made prior to locking the ipad, you can restore from backup. Only changes made since the backup was made will be lost. Any purchases can simply be downloaded again, but any data associated with those purchases will be lost. As noted by Roy Rob, Apple can do the restoration for you, but they can't do anything about your data. Hope you have the backup.
If all is lost, and you don't have a backup, you can at least retrieve any photographs and videos by plugging the ipad into your computer, and browsing to iPad/Internal Storage/ DCIM in Windows Explorer. This works even if the iPad is locked. (We've tried it when this happened to another member, and it works.)