Well, here is a thread that had many Karbonn stock roms, with a flash tool included.
> Karbonn S9 > K9 General > Karbonn Mobiles All Stock Roms
You can ask in that thread for any help with this process.
As far as your actual issue, you may want to ask here before
attempting to return to stock.... Perhaps someone may have a simpler answer...
> Karbonn A21 > A21 Q&A, Help & Troubleshooting
Again, I would ask for help there before restoring stock. May be an easier solution.
---------- Post added at 03:00 PM ---------- Previous post was at 02:56 PM ----------
Also, I may have misunderstood your issue.
If your device works perfectly fine, but you just wiped your internal SD... Pics and all that.... Returning to stock is unnecessary. You've just lost your personal files.
You can try to recover the deleted data, but I've not seen a lot of success with that.
See what the members in your device section think. (the last link I gave you)