When changing the face of the phone, it should not have any effect on the data on the phone. Unless the phone is erased or a "Hard Reset" is done on the phone. If that is the case, there is really no way to get them back.
If you had your phone synced to a Google Account, then you may be able to retrieve the data from there. At least the contacts. However, that is no guarantee that the images associated with those contacts was saved (it often isn't) and the general phone syncing doesn't usually save photos, unless you set it up to do so.
If you didn't have it set up to sync the photos with the google account often, then they are gone as well.