Hi Elterio Delgard, first of all, yes, it's totally possible to do all these things in gimp! To help you further, it would be great to know, what sort of roads, borders or icons you want to make for your map. I guess it's for your project merging and redoing the six maps of yours? (i haven't commented on them yet, but i really like them a lot! )
The roads i made for some of my maps where just made with a hard round brush with the spacing set to ~200. It's a pretty simple way to do this. For borders you could do something similar, or work with paths in gimp. You can stroke the paths with different line styles (..... or ----- or - - - - or --- --- --- )