They came from Gmod, I have been unable to confirm the original producer because the models are available from several different sources and I'm not sure which to credit. If somepony can find the true maker I will credit the development properly. This is one of the reasons I'm not making them more publicly available is due to lack of proper credit. I did not look heavily into the source of the models so far as where in the game they were used, since I was only interested in obtaining the models for conversion, and I don't even actually have Gmod. I had a fellow pony (ah, the magic of friendship) download them for me, I then converted them and saved them to a folder.
I don't know the relative difficulty of the prints either, some of the parts, particularly thin pieces of intricate rod work, may tend to fall or break off, such as the signs and decorations on Sugar Cube corner as pictured. I have not messed with or upgraded the files to work better with the printer yet, so depending on what machine you have and your experience level you may need a simplified version of a file. If I actually get any interest here I will look into upgrading the particular files I get asked for.