I have a collection of .sig files in a directory/file. Can Pine use them to generate random signatures?
No. However, because Pine can accept output from a program, you can write a shell- or perl-script to generate the random signature and send it to STDOUT. Pine can use that. For further information on signatures (including several scripts that do the above, and instructions), see my signatures page at http://www.zrox.net/Mail/Signature/.