What would happen if IMCDb had carriages too? As in horse-drawn ones, not train carriages. I've just watched a film and the carriages are making me think about asking this question
Brands like Robinson & Cook and their models will finally be classed as a vehicle, even if their horsepowers are 1 (literally)

Well , if what i saw in Lucky Luke is true , you can at least go to 4 horsepower...

One of the criterias is the vehicle has to be able to move under its own power .. or at least was able to once it has left the assembly plant for the junked / burned / crashed ones so carriages are very unlikely to happen

So if I wanted this, I'd have to make my own website?

Yes, because it won't be added here.
And I have doubt these would be easy to identify with make & models, that's not as commonly known and recognizable as vehicle makes & models.

We have enough trouble identifying older (pre-1932) cars because many looked alike and all people who directly associate them are either dead or belong to so niche circles that they specialise in one particular brand of car only. Horse carriages are even more niche and I doubt many car people associate with them anyway.

So imagine the futility in this predicament.