Not merely tin (or other sorts of metal) roofs, but any smoother kinds of roofing material, such as tiles or slates. The idea is to substantially roughen the surface in some fashion - using rocks or logs sometimes (still to be seen in the Alps today in places, for instance). Reason I suggested them is, and depending on the snow thickness, they can break-up the appearance of the smooth surface of the snow seen on the roof symbols currently.

Thatched roofs tend to be pitched steeply enough to shed snow (and water), thus snow shouldn't accumulate as much on them (in parts of Japan subject to heavy snowfalls, the thatched roofs have a particularly steep pitch, for example). This isn't so much because thatch can't cope with the snow or water, but because thatch is usually lighter than other roofing materials, so may not be sufficiently supported by the underlying roof structure to carry the additional weight of substantial snowfalls.

Assuming the tunnels and caves have been burrowed into the tree, you might want to start with a blank sheet and draw the tree-rings onto that first (and maybe add the current outer bark layer as well, to fix the tree's size), so it doesn't look as if the rings have somehow retrospectively fitted themselves around what would have been nonexistent internal features when they were laid-down. (As drawn, the web and misty (?) caves would have been in the air outside the original tree when the rings were being laid-down, which would have been tricky at least, I'd suggest!)

I seem to vaguely recall we may have had this conversation previously, but the mountains look a little insubstantial right now, as if many of the arête limbs are only paper thin. I appreciate that wasn't necessarily what you were asking about right now, but it is what first occurred to me!

Zooming-in to the enlarged image, I agree with the notes made earlier, where it looks as if the canvas effect is more pronounced on the paler colours, and not at all (as far as I can tell) on the water. Oddly though, the effect is quite obvious on the tree symbols, which is a curiosity, given they're the darkest objects on the whole map. That could suggest it may be more an issue with the texture on some of the bitmap fills which is causing the canvas effect to disappear, rather than simply the darkness of the hues.

I'd agree that it would be useful to have the canvas effect as an option, rather than a fixed default.

Just to be contrary (well, not JUST...) I rather like the pale desert, but then I can see that would be interesting to use as a cloudscape texture (especially the way the mountain peak seems to be coming up through it), which I suspect may not be everyone's first choice as a setting.

☁️🏰☁️

Not really seeing too much looking "wrong" with your map, to be honest.

As with most styles, there will be things that seem to work better than others sometimes, and it's often just a question of knowing what options there are, and what (sometimes quite small) tweaks will help make things look closer to what you were hoping for. Sue already covered your points regarding forests, settlement placement, and terrain fill blending, I think.

For your point 3, symbol scaling, sometimes the "correct" symbol scaling just doesn't look right - or maybe not for all the available symbols - so you simply have to rescale the ones that don't look so good to fit more with how you envisaged them looking at the scale of the whole map (not zoomed-in though!).

Point 5, unknown areas. You could add areas of a standard terrain fill with no symbols or other features, and maybe add a new Sheet with a pale single-colour polygon - like a grey or white - drawn over the unknown region, and add a Transparency Effect to that, perhaps with an Edge Fade as well. Or you could try a Blur Effect on the terrain fill itself - again set it on its own Sheet so it's not ALL the terrain that does this! Blur can make the file uncomfortably large if used too frequently, however. Just trying things out with the Sheet Effects is always worth doing, so you get a better feeling for what they can do. If there are terrain features that must be in the region too, you can also partly hide them this way. It really depends what you want the area to have the players might know about in advance.

They always were Quenten; just becoming increasingly difficult to conceal that fact 👽️🦑