You're not clear whether it's the web client or the script that has a problem accessing the files. Also, you gave no indication as to how you arrived to the conclusion they cannot be found.

Under Apache, all files (including images), are treated as executable in a ScriptAlias dir. cgi-bin is usually such a dir. The images don't have the executable permission set (for obvious reasons), so you should get a 403 Forbidden error, not a 404 Not Found error.

If it's really the script that can't access the files, the two most common problems are 1) incorrect permissions, and 2) making assumptions about your current work directory when using relatives paths.