Try this one more time.. upgrade from 7.15 to 7.26 now images are missing. Will not take new image

Did you read the update notes? There are a couple of major ones to be aware of, the D 7.24 with the .htaccess files, and possibly relevant to you the file path changes for D 7.20 discussed here https://drupal.org/drupal-7.20-release-notes. Generally this does not break image paths, so I have not looked into it deeply, but if clearing Drupal's caches does not resolve your problem you should aware of this issue as a possible suspect.

As for your words ''will not take new images' you might need to check your permissions. For example if you logged in to server as root and if you used 'cp' command without -p flag to save your files folder then copy it back, it will have changed its owner. That is pure guesswork of course: whatever, the possible cause, it may be worth checking that your images folder is still writable by the web server.