Finding unused image files from web server

recently I have a task. There are many image files (of format .jpg/.gif) uploaded to a web server. However, actually not all image in the web server is shown on the real web site. Now I want to list out the image files that is not on the web site but in the web server, so I want to find a tool that can generate a list of images of a web site, I have found a firefox extention call Link Gopher which may help to generate all links from a web page, but since the web site has many pages, I must do the task page by page if I use Link Gopher.

As a result, I want to know is there any method that can do the task faster, or is there any tool can can generate links of a web site (including all pages of that site)? Really need you guys help, Thanks you so much!!