It looks awesome. I agree, the rivers need a bit more buffer ... and one more thing: is Iceland really so forested?
Inkscape isn't able to handle 80,000 tree symbols. This could prove problematic.
My new approach will be to take the tree and mountain layers, combine them and sort them, then add an attribute with a random value. Then symbolize on that value. Then I'll turn off all other layers and export a high res raster image from QGIS and load that into Inkscape along with vector versions of the rivers, coast, etc and do final composition that way.
80.000?? wow... how many trees are there in Canada anyway? but I must say the result so far looks pretty amazing! cheers, DJ