This map is looking so good. Great techique for mountans, realistic landforms, beautiful lettering and a true feeling of a 1600's century map. Hard to say what could be better. Some more rivers in the flat areas perhaps?
The projections were calculated and drawn by hand somehow before computers, and I think that requires a lot of knowledge and many calculations. But if you don't need to draw the map in many projections, an easy way is to copy a grid from another map. This is what I did with my map of Magran (still ongoing project, wip here).
- Find an atlas that is larger than the size of paper in your map
- Select a map with the same scale than your map, and from the same latitude as the place in your map (longitudes doesn't matter, naturally, and neither the hemisphere.)
- Place your map on top of the atlas's map. North to north if the maps are on the same hemisphere and upside down if they are on different hemispheres.
- Mark the locations of the lines of latitude and longitude in the sides of your map with pencil.
- For longitudes, the points can be just connected with a ruler (in most projections).
- For latitudes, I measured the distance of the line from the side of the paper in places where they crossed the longitudes and marked them on the map. Then I connected the points to one line with a flexible curve.
- If you like, write labels for the lines in the map. Longitudes can be anything you like, latitudes the same as in the atlas.
The result is a grid of a real projection, exact as in the surface of our earth. Of course, it's only a mock projection, but it looks good. If the depicted area is large, you have to take different distortions into considerstion to keep it realistic.
I've found old cartography textbooks to be most helpful. For example one from the 1950's, Elements of Cartography, they teach in them how to make good maps by hand. There are also information about calculating the projections, if interested.
I hope this helps!