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.

Was it the Glow Effect, or the Outer Glow one, you were using? Outer Glow does need more work to stop it looking like a solid mass outside the highlighted object sometimes, as there are more elements of it you can adjust. Glow usually works quite well without having to do this, particularly for circular objects (Glow doesn't work so well for the corners of angular objects however; Outer Glow is much better for those).

You might want to think of swapping the locations for the Red Sun and Georgia systems, as the red coloration isn't so easy to see against the darker sky background. The yellow for the Georgia system should still be fine against the darker area where Red Sun is currently.

Looking over the various CC3+ fills available for dungeon/battlemap use (in the Bitmaps/Tiles/Dungeon folder of CC3+), it seems although there are a number of random stonework options including in DD3 already, as well as the Bogie and Dundjinni free collections, something like the cobblestone arcs isn't. There are a few options for adding patterned stonework floor textures (there's a herringbone brickwork option in DD3, for example), and rather more for using individual patterned tiles that can be fitted together in squares separately (think medieval cathedral floors), but I suspect the arcs make creating a seamless texture that will properly tile too difficult. Or at least, nobody seems to have done it till now. I could have missed something though, so please feel free to leap in to say so!

If you're going for a more natural growth look, it may be better to use smoother lines for the tunnels and caves. The fractal edges right now is what made me assume they'd been tunneled in.

And don't forget the third dimension - no reason that couldn't be an ascending, or descending (or both in different places), spiral, rather than one on a more or less single horizontal plane.

Some of the expanses of farmland look like scaled skin - civilisation built on the back of a dragon, perhaps? 😉🐉

You could perhaps fade-out the outer edges of the whole, maybe using an overlay sheet with a large Edge Fade Inner Effect, to get away from the "edge of the world" look of too much in the map's centre compared to the periphery.

Text in banners might be too elaborate for this map; probably worth trying just text at first (you can always add banners later if that still seems needed).