Hey Carl
I've been looking at your maps, and I think I understand partly what xCali was trying to say. Part of the issue I'm having... is that the landmasses are too chunky... to blockish.
Best way that I can explain it... it's almost as if you had a piece of paper that was your original land mass, and you tore that piece of paper up and spread it out to make your land masses.
Fault lines do this in some what a similar fashion... but even then, the landmass didn't start out with a straight edge. Also... there is erosion to consider. Landmasses are always changing. Volcanoes, over time, create new landmasses, or add to existing ones. Erosion takes a way from the landmasses. Fault lines crack and break apart, separate and create new fault lines which continue the process. Flooding causes lower landmasses to be engulfed, so that only their higher altitudes are visible in the shape of small islands.
If you don't want to pay for a program to help you with your mapping, may I suggest Gimp? A lot of people here use it, there are youtube tutorials for it. And from what I understand, it helps create some really nice maps! I would also agree with xCali's suggestion, and look at other world maps, perhaps check some WIP's in the world mapping section, to get an idea of how others draw their land masses.
I think once you get the hang of that, and tighten up what you have here, it will be a fantastic map!