Thanks for the welcome, jbgibson!
I kinda did what you suggested already. The 14 coastline sheets were merged into one big, hi-res document. That was when I found out that I was aiming too high with the resolution and had a conversation with friend. He's a filmmaker and knows his way around a little regarding ppi and that stuff. He asked me if I wanted to plaster a wall.
I created a new document, size A0 (9933 x 14043 px at 300 ppi) and pasted the original outline into it and rescaled it. Much better now.
Once I have general idea of how it will look like, I'll finish a worldmap first, so I have a good overview. After that I'll be doing regional maps.
Well, the size of this world is roughly Europe including the Middle East. So about 5000 miles from north to south, the top regions being almost arctic.About this world map you're showing us early stages of... Where does that fit on a globe? Most projections are going to be wider than they are tall. Decide on a reasonable projection for your main world map - based on the arrangement of land masses one might suffer less distortion than another-- or at least less awkwardly placed distortion. When you do generate a reasonable world, don't clip the view so close to the land masses. Some small-scale maps you're going to want plenty of ocean shown, whether to focus on ocean characteristics, or just as a convenient no interfering place to put legend info. Just search go the word "projection" and read the first 25 threads that mention it. Some will have good tips - particularly commentary by Hai Etlik, who is one of our resident advocates for plausible geodesy and projection choice.
You *could* call what you already have a world map, if that world is mostly water that you aren't showing; also if what is shown only goes to mid-latitudes. Hmmm - in other words if it isn't a comprehensive world map but essentially a regional one ;-).
Thanks for the tip on projection, but I don't know if I'm going to need that. It's a flat world, with no curvature.
And it IS a comprehensive world map, at least for this one!