Tile groups make placing large items quicker, volcano's, cliffs, ice cliffs at the top and bottom of world maps, and there are large brush blocks for making sand, rock, volcano terrain easier and more random (albeit those stamp pads, if you want to call them that, could be much larger in my opinion) Open the mapper and open a OP2 current map and you should see that.
I am hoping you're asking because you want to make the mapper more productive (in that case some suggestions could be made on that part)
Hooman would be able to tell you the ins and outs of the code I'm sure, and Leeor has experience with mappers as well. And most people are on the same page in believing that this mapper could use a healthy update.