I think the ideal would be to do this outside of Pd with a dedicated software (like batch file renamer on windows or anything from the appstore on mac). if, for some reason, you really wanna do this within Pd, then you should take a look at the attached patch: it's a loop recorder that can save audio to files in a dedicated folder and name these files sequentially. You can probably modify it to do just what you want. But were talking .wav here, I'm not sure what to do with jpg's. Anyway, hope it helps...
 
note: the "choose directory" function on the patch requires you to click on a file in the desired directory. If there is none, you can just create an empty notepad file or something.