The small ones are from 'Opaku' - Sonobe Souan - himself, they are parts of the 'Scene changer' of his homepage. Start from http://www.mars.dti.ne.jp/~opaku/zigzag/railway/e/, select the 'Samples' pages from the left side menu, then select one of the scene changer pages.
The bigger - mostly wider - ones, usually containing a bridge, are from the https://fukayoid.main.jp/trainkit.html homepage. This page has no english version, only japanese.