Yeah it's not an interactive object, it's just a static prop.
I really like the shadow underneath and the faded backside!
The wheel base is based on the image from the permanent way wiki. I thought it looked like it worked like this:

Rails in blue and wheel axle in red.
With the large guide wheels on the inside of the rails and the outer wheels connected to the inner wheels via a bevel where the rails run. But maybe that doesn't read that well. I tried moving it up 1 and 2 pixels but in my head it looks best with the original height but I'm probably biased of knowing what I tried to draw xP
Also made a version with a pile of mined rocks and a version going up/down.

I gave the gray wood a shot!

Also did some more supports, both crossing the path to uphold the roof and along the walls holding loose rocks in.
Since there are 3 tile high walls covering all but a 2 tile wide strip of the walkable area, I thought about making all vertical spaces atleast 6 tiles tall to show more of the ground, but the walls can still cover the player so either way I'll need a solution for that. I'm thinking of adding a higher collision line for overhanging south walls.
Here the red lines show the normal walkable area, and the lowest red line would be replaced with the green line to always keep the player at least partially visible. What are your thought on that?

Hehe that makes even more sense, so obvious after you've said it too xP
I will go back to wooden pile terminal, but I think what you said about not using good timber makes sense so the new one is just a small pile of slips. Also made a new mockup more akin to what I imagine the "miney" parts of the mines will be like, straight corridors with tracks to try out some of the wall and roof supports. Although in the game they will connect to more "cavey" parts where they found a good concentration of ore and just dug out in all direction where they found ore. Might not make sense mine-safety wise but in a game I think it will be nice with alternating tight and open combat-scapes.
Got a little excited and skipped making minecarts to try out making a support beam

I thought about doing the rail piece to select direction where the tracks split but it felt like it would clutter it up to much and decrease the readability. But maybe I could add openings for the wheels so they at least have a place to roll going either way and leave the mechanism of selecting a direction to the players imagination

The darkening on the logs is supposed to be water damage from being in a damp mine. Sort of like this:
Spoiler
Darkening at the ends where the fibers are broken and water can enter easily. But having them banged up a bit where they meet the track is a great idea!

And I think a pile of rocks to stop a mine cart might lead to a very short lived mine cart, maybe wood to dampen the impact and rocks behind to add weight and rigidity to the logs?

Yes support beams are on my list of features to add, both as alternative wall sections and as crossbeams holding up the roof, just haven't gotten to them yet