Ish: By "frame lines" I simply meant a rectangle that forms the border of your page, which can be as thick as you wish. Sometimes a really thick one can form the main border, with a thinner line (or 2, or 3...) as the rest. It's a simple technique that really has only one purpose: create a non-distracting border.

If you are shooting for a realistic map, and if you have the original GIMP layers/files (or, if you feel like playing around a bit) I would kindly recommend you redo a few of the textures your friend used. For example, the forests look a lot like swatches of rug (I assume this was the canvas filter on green or something); break that up & do something less regular & less "filtery". Ditto on the grasslands & the desert.

Also, the colors are a bit too pastel & too regular for a realistic map. Add variations--especially darks--to the land & water. The mountains, I think, are basically fine though.

I would finally recommend that when you're all done you use some sort of filter to mute just slightly the sharpness of the entire map (ex: blur or noise); hard, crisp edges rarely look realistic INHO.

I hope that all helps at least a smidgen!