Assuming you’re using Bash…
In that case it’s better if you don’t use P12801{00..90}.jpg \ at all, and instead rely on "$@" and then use the script not from command-line which can be cumbersome, but from a graphical file manager. E.g. make a selection of image files in Dolphin of Thunar or PCMan or whatever file manager you use, then right-click on them and “Open with” the script.
To get you started, you are interested in parameter expansion, specifically "$@"
http://mywiki.wooledge.org/BashGuide/Parameters
http://wiki.bash-hackers.org/syntax/pe
This script:
#!/usr/bin/env bash
printf '%s\n' "$@"
for f in "$@"; do
printf "%s\n" "$f"
done
which I saved as /tmp/foo and set chmod +x /tmp/foo, will print the same list of input files twice:
/tmp/foo "image 1.tif" "image 2.jpg" "image 7.png"
image 1.tif
image 2.jpg
image 7.png
image 1.tif
image 2.jpg
image 7.png
The for loop lets you do things to each positional parameter on the fly.