If the photos were taken with the iPad, copied to it via the camera connection kit, or saved from emails/websites then see this page then your computer should see them and be able to copy them off : http://support.apple.com/kb/HT4083
For photos that were originally synced from a computer you will need a third-party app such as Simple Transfer which can copy them off via your wifi network. But as photos are 'optimised' when they are synced to the iPad, any that you then copy back to a computer may not be exactly the same as they originally were on your computer. If it it's this type of photo that you are trying to copy off, then have you not got a backup copy of them on, for example, an external drive ?