If the processing you require is something like renaming 1.JPG to MyPicture1-320x480.jpg, and 2.JPG to MyPicture2-320x480.jpg, etc. then if you are using the Bash shell, you could change to the directory that contains the files and use something like:
i=0; for n in *.JPG; do mv "${n}" "MyPicture${n/.JPG/-320x480.jpg}"; i=$((i+1)); done; echo "Processed ${i} files."
(The above can all be typed on one command-line.)
Or if you want to put it into a script, it would be easier to read and understand on multiple lines:
# reset counter variable if you want to count the number of files processed
i=0
# loop for all files in current working directory that end with ".JPG"
for n in *.JPG
do
# rename (move) each file from the original name (${n} is generally safer than $n)
# to a new name with some text before the original name and then with the end of
# the original name (".JPG") replaced with a new ending
mv "${n}" "MyPicture${n/.JPG/-320x480.jpg}"
# increment the counter variable
i=$((i+1))
done
# display the number of files processed.
echo "Processed ${i} files."
If the processing you want is different to this, you might need to edit your question to provide more details.
