So here is my take...Tour cars are like smaller buses. Land Yachts...
Also....
There is no NPC factor in this game yet, no traffic, no waldo to find either. Open TTD has a mod for a single man on a horse OR a police car. They really serve no purpose other than to be little items of interest on the map. Interestingly enough, with both of those they are themselves considered a passenger so they technically pay for themselves. I was surprised by that. Anyway, Kinda fun "Where is it now" on the map. Hearing that cop car in the distance is funny... (but can be annoying too since it rarely shuts up!)
Now... for me, for fun and immersion, I am running a tour company in my game. I believe in customer service and attention to detail. We don't believe in those huge over-packed buses. We like those early themed tour vehicles. Another example is to look at the Old... Yellowstone Tour Bus.
Anyway, either way you go, I am sure I can use something you have.. Thanks for the work!

Definetly do plan to add more vehicles! Since finding old stuff is kinda hard I appreciate the suggestion of the Stanley and other steam vehicles, definetly would love to do some of those. Though I don't really see the point of making proper cars as they woudn't really have a purpose apart from looking cool but I could be persuaded

So here is where I am at with your mod currently. I decided to have simple tour routes and tour buses on dedicated routes. They will have waiting stops so that I can do a first person ride like it is a guided tour of the area, stopping at overlooks and other points of interest along the way. I decided motorized, slow, and novel was the way to go. Your little bus is perfect. I plan to force passengers to go on tours and pay me!
Anyway....... Would love to seem some classic American and European road cars from the 1920's-40's... large passenger cars or the old cross country expedition cars IE: Drivers and 8-12 passenger. Even and Old Stanley Steamer would be cool! Old Steam tour cars!
What would be awesome too, is if you could add to or have a complementary Mod that has a small garage that supports only your old vehicles. I would love to have one I could use as the garage at my Tour business.. lol