Apparently you tampered with the Dock.app in CoreServices to try to change the dock appearance. The full path to the dock is:
If you have a backup of the original Dock.app I suggest you replace the current one with the original. Drag the "damaged" one to your trash and then drag the good replacement into the CoreServices file. Then killall Dock.
Note, I am assuming you got that stuff from this web site. That page has a link to download the original images that presumably you replaced in your Dock.app. So if you don't have a backup try restoring your Dock.app with the images provided on that page and follow the instructions there on how to do it. Good luck.