You are reading this message wrongly. What it is telling you is that multiple pages on your site have duplicate TITLE tags (the ones in your HEAD). Since they are duplicates, it means that you haven't provided anything to distinguish one from the other. This means that users searching Google will see nearly identical results for both pages. WMT is suggesting that you page something different to distinguish them. It seems like what is happeing is that you are using the same title for multiple pages. Maybe you can just add ' - Page 1', ' - Page 2', etc to each of those pages.
UPDATE: OK, it appears that all of your images have been uploaded twice. You want to delete all of the images which end in '*-2'. After you've done that most of those duplicates should disappear. You may need to remove them from the Media Manager in WP to make them fully disappear. If you've linked to any of these duplicates then you'll need to update your links in your blog as well. I hope this is something that can easily be taken care of manually.