Today I filled in the outline, created jagged coasts in the south, and did everything from climate to currents to geology to vegetation type. I fixed up my mountain chains, painted rivers and even cracked 300 MB filesize, til I split it up.
I have produced a large-resolution greyscale map suitable for printing, and was surprised to find a neat tool within Photoshop called "Zoomify".
You can see the result here: http://world-makers.com/SNRM_ZoomMap1/SNRM1.html