I Reinstalled Windows 7 via image recovery and overwritten a drive C without backing up data on drive c. After installing windows i recovered data of C drive through easeus data recovery tool. Although i have recovered all the files yet pictures are not viewable in Windows Photo Viewer. Anyone can help me on that???

Maybe you need to used different view picture software to make sure is the picture ok or not.
How big is the picture, go to properties to make sure the pciture is not 0 kb. If it is 0kb mean the picture is not working.

Usually, files like JPG images can be checked by using both the size, as indicated. When I need to recover files off a bad drive, I use the JPG header and footer to mark the beginning and ending of the file. Other times, I use just the header and read in the next 1MB to ensure I have the full Image. When you recover, make sure you have the proper HEX header for the filetype. e.g. for JPG files, the hex header is FF D8 FF E0 and the footer is FF D9.