Yep, I see what happened. You erased the white - which is the same process as 'painting on' the parchment. You can see it in the brush strokes around the edges - those brush strokes could only have happened if the parchment was painted.

I really like the hand drawn city and the houses. I think you need some more variation on the trees if you're going to sell those as being hand drawn. At the moment they're identical in size and shape. Perhaps a little bit of size and roundness jitter would break that up.

Nice map - thanks for putting it up!