First off, let me just thank you for a great plugin! It fits my needs perfectly :)
I do have one main issue though: I have multiple sigs for various uses on my blog and it gets difficult trying to remember exactly which numbered shortcode corresponds to which sig, which means I have to go back to the list of sigs to check the number and come back to my post to enter the correct one.
It would be great if while we are setting the number of sigs in the settings, if there was also an extra field so we can give each sig a custom shortcode.
Another plugin I use - Widgets on Pages - has a similar setup, which makes it very easy to manage.
Thanks again for a great plugin!