OK-I figured it out, an ".img" file is basically the same as a ".iso" file.
To make one, take any iso-let's say goblinx-2.7-Micro.iso, extract the iso contents to a folder-right-click on iso-select "extract here", a folder named goblinx-2.7-micro will appear. Now, go into the folder and then into the "goblinx" folder. here you will find a script called "make_iso.sh", move or copy this script into the "boot" folder(otherwise it won't work). Now, right-click on the make_iso.sh and select "properties", then select "permissions", check the box that says-"allow executing file as program".
Now, double left click on make_iso.sh, a box will appear that says "run in terminal/display/run", choose run in terminal, a terminal will appear asking you for the name of the iso
Target ISO file name [ Hit enter for /home/bz/Desktop/boot.iso ]:
instead of naming it myiso.iso, name it myiso.img and a .img file will be made.
Actually I just figured out that just renaming an iso file to .img changes it-der?