I don't have a 3D printer, but I might get one someday. So I like to look at props and terrain people are designing now and then. You aroused my curiosity. I took the list of props and terrain that was compiled a while back on this forum [http://dmscraft.proboards.com/thread/1579/find-dungeon] and went looking on Thingiverse. First I removed things from the list that you wouldn't reasonably make by 3D printing, such as wall paintings or forks and spoons, or that would require very elaborate assembling of set-ups. I found almost everything on Thingiverse, including multiple versions of a lot of them.
And more, too. Since the list was for things you might find in a dungeon, it didn't include tents and carts and such, which you can get on Thingiverse.
And the point of all this is:
I think that basic models of almost everything a DM might want are available now. If a DM wants something more specific - well, the 3D prints still have to be painted. You can do a lot of detailing with just paint on a basic model. And if someone tweaks a summoning circle model to print it with a different set of runes, they likely wouldn't consider it enough of a change to warrant posting.
We might see more different fountains and statues. And there is still some building design going on, although you said you aren't interested in those. Also, there is still a shortage of suits of armor and piles of animal bones, so there's a little opportunity yet for new designs.
It was an interesting exercise - I particularly enjoyed finding the animal trophy heads!
I guess I have been using Thingiverse for quite awhile now and I do get that many items are there, but just to give you an example, there are partial market place things, but I wanted a fuller selection of items for the market. I ended up making my own items because what was available was limited. I wanted a miniature sundial. I ended up making it because it wasn't there. I don't see a lot of fields growing type tiles so I will either purchase it or have to make it. I didn't see a lot of interconnecting roads that I liked with details so I made my own back in July 2017 and even earlier. I know this has changed recently with the addition of Devon Jone's work in November and Donald Stouffer's work in October. I would like to think I might have influenced this with my own pieces. Interesting that I was going to mention interconnecting bridge tiles and just this month Devon Jone's just released new tile sets. Still would like more variety of items, but it looks like a sudden surge in new releases might resolve some of the issues I am seeing accept interconnecting farm terrain tiles and detailed flowing river tiles.
Oh and you can do paintings by superimposing images over a tile and doing the depth. Obviously you are limited on detail, but it is possible to duplicate say a Mona Lisa if the size is large enough. That's what I did for this Velocirator fossil tile.
Velciraptor