Included with the original release of Magic Carpet, but oddly left out of Magic Carpet Plus, was this cool utility that allowed one to make their own multiplayer maps from image files (with certain restrictions of course). So, here it is for those interested in having their own terrain in Magic Carpet :

http://www.ag.ru/games/magic-carpet/patches/6915
or
http://new.patches-scrolls.com/patch/2564/27381/46355/download

The instructions (from http://www.ag.ru/games/magic-carpet/cheats/4703) are as followed :

"USING MAPHACK

With MapHack, any PBM file (that is, a compressed LBM file) on
your system can be used as the basis for the landscape of one
of Magic Carpet's levels. Any 256-color PBM file will do; it
is automatically re-sized to 256 x 256 pixels.

To use MapHack:

From the Carpet CD type MAPHACK, followed by the PBM file name
and press Enter (remember to specify the path).

Example: MAPHACK C:\CARPET.CD\EXAMPLE.LBM

When you run Magic Carpet, this picture is used as the first
level map.

To re-set Magic Carpet to the original settings:

Log to your hard drive (C:) and type del
C:\CARPET.CD\SAVE\SCANNED\RMD and press enter. The game map
returns to normal with the LBM file removed."

The link above @ Patches-Scrolls is dead. Here's the new link :

http://www.patches-scrolls.de/patch/2564/7/27381

how i can create a new PBM file ? i want to create my own level.

and how can we add this command line in the dosboxMC_single.conf file of gog

Any paint program that can save as .lbm or .pbm will work. .lbm is originally associated with Deluxe Paint 2, which you can find copies of elsewhere (running and using DeluxePaint is beyond what I can provide support for). This program might help :
http://settlers2.net/documentation/graphics-files-lbm/ If you can't figure it out, I'll elaborate on the exact means to do this later. It's actually very easy if you understand DOS and navigating DIR's well.

The reader's digest version is you must do the following :
- Find where Magic Carpet is installed, and put maphack.exe in the same DIR as where ever the DOSBox commands for mounting C are.
- Comment out the line to run magic carpet (carpet.exe), and add maphack.exe (with the appropriate parameters for the file you want to convert into the game). You add a # to the start of the line to comment.
- Add a pause command on the net line after maphack (literally just : pause)
- Convert the file of choice and copy into the same DIR as above (makes things easier).
- Run the DOSBox for Magic Carpet, which will in turn run maphack. The pause above will let you see any output from maphack including error or success messages.

The file will end up looking something like :

# carpet.exe
maphack myfile.lbm
pause
exit

- Edit the DOSBox config again, comment out maphack and pause this time, and uncomment carpet.exe :

carpet.exe
# maphack myfile.lbm
# pause
exit

- From there you should be able to play your map



It sounds like more work than it is, again, if you know DOS. If not, you'll learn in the process.