A quick handy little way to add a prefix to files in bash (taken from here)
for f in * ; do mv "$f" "PRE_$f" ; done
In my case I wanted to rename all sub-100 filenames to have an extra zero so sorting played nicely with filenames beginning with 100+. To accomplish this I found about the rename command (thanks to this site.) The command I used to enforce natural sorting was the following:
rename 's/\d+/sprintf("%03d", $&)/e' *
The command looked for anything beginning with a number, then used sprintf to make the number 3 digits. The asterisk instructed the rename command to work on every file. Success.