the ROM of the neo geo game Riding Hero seems to fill in most of empty spots of the tilemap with little smiley faces

it sure isn't fun to try to play through an arcade racing game when the ROAD isn't working

The game is supposed to look more like this but the road is done using some raster effect that's not being emulated properly

Fun fact about this game: It supports "LAN play", so you can have several Neo Geo systems (either full MVS cabinets or the home AES systems) and play against other players, each on your own screen.
How's it do that, if the Neo Geo doesn't have a networking connection? Well...

They included a 3.5mm cable in the packaging! Does this mean you hook up the sound output jacks, and it does some kind of networking-over-sound system?

NOPE!

They built a jack right into cartridge itself, so you connect the cartridges together using that cable.

Keep in mind that the cartridges in a Neo Geo MVS are in the middle of the cabinet, so you'd need to find a way to carefully route that cable out an existing hole (or drill a new one) to hook it up to another cabinet.

The MVS version of the cartridge has two jacks, so you can daisy-chain them together.

The manual explained how to hook up multiple systems (up to 4) but Riding Hero only supported 2 systems, I believe.

They reused the same system in League Bowling and Thrash Rally.

This, btw, is one of the things I love the most about cartridge based systems.
The console you're targeting doesn't have the ability to do the thing you want it to?
Fuck it, shove some chips and connectors in there, why not!

I've done a whole thread about those add-on chips included in cartridges, specifically about the SNES: https://twitter.com/Foone/status/1177644211790729216