The guild has about 5 sets of distinct types of mappers. One of these groups is the 3D terrain group which is where I sit mainly. I dev an app where you enter a rough terrain and it chews on it and spits out a better one using a geological simulation to attempt to enhance it or make it higher res than the input. Waldronate on here devs Fractal Terrains and Wilbur. In terms of app devs we have several more though they post very rarely. Su-Liam also does a lot of terrain modelling with noise functions too. Monks is making middle earth using contours and there are others which hand draw or use SRTM / Lidar bits to make maps. All said tho, its still a pretty open field and one where new techniques are welcomed because as yet there is no bit of software or method which I know that can generate really realistic terrain of a wide variety of types. Even once done then the discussion starts about the vegetation and climate models so thats another area we like to listen to.
The posts about this kind of stuff are scattered about the guild and it can be hard to find them. I have a keyword index in my sig where you can look up 3D (I should add DEM to that list). Su-Liam posted some interesting things in the following link and made the guild rank highly in google with the word sperm - which will only be enhanced with this post too
I would be interested to hear about how you like to do it with Leveller tho.