Mr. Pseudo has given you the .grf file.
There are multiple ways to add or replace a map.
Merging myRO.grf and newprontera.grf using GRF Builder.
Step 1. Open your myRO.grf wait for it to be read.
Step 2.
Step 3. Replace your myRO.grf in your RO Folder.
*I think the "NEW PRONTERA" map works on 2013 clients.*
Since mine is
// see conf/battle/client.conf for other version
#ifndef PACKETVER
//#define PACKETVER 20130807
#define PACKETVER 20120410
I got an error.
.
Manually replacing/adding the map files to your data folder.
Step 1. Open your myRO.grf
Step 2. Click "Extract All".
Wait for it
Step 3. After this click on "close".
Step 4. Open your desired prontera map, extract it, and replace it all. (In my case I'm going to replace my prontera with Olrox's Fall Seasons Prontera)
Step 5. Open GRFBuilder click on "New" for your new grf (I like to make new copies in case there will be a problem).
Step 6. Click on "MERGE DIR" look for the "data" folder where you placed the new prontera map files.
Step 7. Copy/replace your myro.grf in your RO folder.
Step 8. Lastly it should work.
*switched from summer to fall*
Map credits to Olrox
Mickole's post in Prontera Error was marked as the answer