Some common image-related problems:
* image referred to by its Windows name (on the PC) and not by its Linux name (on the server)
You've looked at the gallery code on the server and it says "pics/1.jpg" and not "C:\Documents and Settings\..."? This is common when using site or page builders such as FrontPage.
* image was never uploaded
cPanel > File Manager, navigate to the directory and see if the file is there. Perhaps it ended up in the wrong directory?* Linux is case-sensitive, so 1.JPG is different from 1.jpg. Windows is case-insensitive, and treats the two as the same name.
* image was corrupted during upload
It should have been uploaded in BINARY mode. Did you force ASCII mode? Use your browser to call up the image for display (http://www.yoursite.com/gallery/testgallery/pics/1.jpg) and see if it displays correctly.* your gallery code is running in some other directory than you think it is, so
pics/ is not directly under the directory you're running in
* you have hotlinking protection on, forbidding your site from loading image files
If you add a subdomain or add-on domain, be sure to add it to the "permitted" list in .htaccess.