I have cropped the desired portion, converted it to greyscale and removed labels, latitude/longitude lines, and edited the rivers. If you use tropical climate for the map, large deserts will appear on the coast. You can remove them by CTRL-click with the Landscaping>Desert tool. I am not sure how to remove them otherwise.
This is a test version which I will improve upon promptly. Many mistakes indeed, I think I drew some of the borders as rivers, you might see ghostly remains of words on the map
The map is centered on Surinam, and includes French Guiana, Guyana, a part of NE Brazil, and Trinidad. I am thinking of expanding the map to the west and south to include space for the large cities in eastern Venezuela and also for Brazil. I left the stars on to locate the capitals Georgetown, Paramaribo and Cayenne easily, you can remove them with scenario edit.
You can play it on 2048x2048 for best, smooth look (although the image is not exactly this dimension). You could try 4096x4096 if you want to simulate the remoteness in the interior of these countries, and make river crossings by ferries more realistic. I recommend a max height level of 21-25. I might release a scenario to this map with all major towns and cities, using the American Roadset, TTRS and FIRS to name a few.
This is my first attempts at a heightmap, tell me what you think
To keep things 'remote' I would probably have to only include major cities, but I'll see. To be honest I'd be more interested in making scenarios of specific regions in South America like maybe a map to include Argentina, Chile, Uruguay and Paraguay for example, then another to include Brazil, Peru, Bolivia, etc. and so on