The carriage looks really good - and the concept is original to say the least!
The only things that seem off (to me) as it is, are the levels of detail - there’s plenty of detial in there, but some areas seem to have more than others. Not a bad thing in itself, but it makes it tricky to assess the modelling as a whole… Some close ups would be really cool 
The other thing is the flag, make it blow the other way - think of the speed this (these?) fellas will be kicking up!
As Zr0-1 said - Wells Fargo, very nice touch 