You can just put all your files into a sub-directory and jar the directory.
Here is an example:
Assuming .class files is in "currentDir\com\test\", pictures in "currentDir\com\pic".
You run "jar myFile.jar com". Then all files under "com" goes to myFile.jar.
To read a file, you can just say
InputStream i = getClass().getResourceAsStream(fileName);
Or you can use "File" to open it.
To bsd:
Make sure your java classes are in right package. In this case, all java files have to be in the package "com.test".