Not sure it will work well enough, but for the pit, you might try drawing a thin line around the top edge of it on a Sheet above the rest of the pit, and apply the same Wall Shadow Effect to it as the rest of the level's walls already have. That should shade the pit the same way as the walls, and hopefully make it not so flat.

If you've a suitable image you can and want to use (importing an entire spiral galaxy will likely crash your computer ?), and it's available to you as a standard image file (jpg, png, bmp), you can simply create a new Sheet in your CC3+ drawing, and then import it into that using the Draw - Insert File command from the drop-down menus. Give the Sheet a recognisable name so you can find it easily when you need to turn it on and off. You may need to resize the image to get it to fit the size of your drawing properly, but that's fairly easily done, if a bit fiddly to get exactly right.

You would probably be best to also set the file image up on a separate Layer too, but that's not essential.

Careful, Jim:

??

This used to happen with new sheets you'd created in any map. If you didn't put anything on the sheet, it would be deleted the next time you reopened the map. That was changed in an update a long while back, and while it does solve the problem that if you don't use it immediately, you'll lose it, it does mean most maps now end up with far too many sheets in, because nobody's ever going to remember which sheets haven't been used in a given map. Plus there's always the danger you'll accidentally delete some critical sheet by mistake that has something on you'd forgotten about if you try to do a cleanup manually.

It would be excellent to have the same possibility to remove excess Sheets at the end of a map, just as you can with Layers, currently. Not sure how practical that would be from a programming perspective though.

Jim, I think your original maps are from the Argan Argar Atlas, which states only that the hex scale is 8 km or 5 miles. All that means is each hex is classed as five miles in size, but that's NOT in any specific direction. This was a very common assumption at one time, when hexes were really just used for approximate distance estimating in games overall (RPGs and boardgames), so it's not a true scale from any one part of the hex to another.

It doesn't help that even some of the original hand-drawn maps of Glorantha by Greg Stafford don't have a proper scale on them, so realistically, you can set whatever scale distance best suits your purposes, and not get bogged down in the minutiae of mathematical precision for something that never had it in the first place!

If you want to investigate further, this topic on the Basic Role Playing Forum (for those unfamiliar, BRP is the base RPG system engine all the Chaosium RPGs use) pretty much covers all the essential details and issues. Even the official published RQ books and maps aren't consistent in their scaling of the same places - which to an extent is fair enough, as this is a game world set in what for Earth would be the Bronze Age!

Not sure if I'm interpreting what you're intending here correctly, but if the paler, sandy coloured coastal strip is meant to represent an extensive, low-lying beach, and the fractal lines are the actual high vertical cliffs, it might be useful to use the cliff lines as the coast, and make the seaward edge of the beach have a less strong outer effects line. If it's a beach, after all, it must be submerged by the tide in part at least some of the time, whereas the cliffs would form the actual coastal barrier.

If Erdan Worlds won't let you do what you want with the mapping, it's probably best to look around for something that will. 13th Age might be somewhat closer to that example map whose style you want to replicate, for instance as a first suggestion. You're never going to get exact matches for everything, of course (unless the source map's in a style PF already has available that is!), so you need to decide what's most important to preserve, and then work around that.

In terms of the Sheet Effects, like Edge Fade and Edge Fade Inner, or others that may help blend adjacent textures, adjusting the size and strength beyond the presets is always worth trying out. Experimentation is key though, as has been said before re Sheet Effects generally, and trying to advise you "blind" like this isn't really practical. You just need to play around with ideas and see what you think looks good. If you run into specific snags, someone here may well be able to assist.

You might also want to try varying the edges of adjacent terrains, so they're not always simple linear features - not saying to use fractals here, just add some extra curves and variations by-hand (like a weak "jigsaw piece" join, perhaps), nothing very finely-detailed. With a strong enough Effect, you'll not see much of the original shape, and it may help break-up the linear junction a bit more.

The blending in this sample map looks like it could work by adding rounded patches of one of the greens over the top of the other, with a strong Edge Fade Inner Effect on the patches Sheet, for instance.

Wasn't able to get along for yesterday's livestream, so have just been catching-up with the VOD tonight instead. SS6 looking good, and I suspect those circled key numbers especially are going to see a lot of use beyond this set alone!

However, I was shocked to see the Hobbit village didn't make everyone in chat smial 😉...

Up to you, but I'd say not, since the place needs a reliable water source, and the area map is truly vast, so small streams and even modest rivers, likely wouldn't feature.

And were-elks will the were-elks get a drink 😉?

[What have I started...]

Mystara rather passed me by @Tonnichiwa, as I'd moved on to my own version of D&D, and other RPG systems, even by the time it first featured, as the Known World (in Module X1 "The Isle of Dread" according to online sources, in 1981). I have gone back in more recent times and looked over some of what was published for the Known World/Mystara setting, though after getting back strongly involved with D&D only when 5e appeared, I've concentrated more on finding past details for the Forgotten Realms setting, because of its intimate connection with 5e from the outset.