I’m building a parking garage in Roblox Studio. This garage will be for the vehicle meshes I make. I have 2 vehicles in here currently but they are not mine. I have them here so I can pick which chassis I want to use for my vehicles. One of them the one with the blue glowing lines is an A-Chassis. Would this be better? If so, could I be sent a link to the real a-chassis? I have a feeling the one I have is not legit. Anyways, here’s an image of the garage. It’s quite bland I must say. Any suggestions? 
As you said, it is very bland.
I would add 1-2 more rows of pillars closer and add parking lines to make it look less empty.
Parking lines are noted. I was going to consider adding big numbers on the wall to help identify the spaces. But 1-2 more rows of pillars closer? What do you mean?
Add more pillars like the ones in the back, but move them up to the empty area so it’ll fill it more. Numbering system would also add a nice touch to it.
I added a door next to the pillar in the far back. Moving the pillar back will block that door.
It can definitely use a lot more pillars inside, aswell as parking lines.
Smaller details but maybe add like electrical boxes or pipes and like colored floor things that most parking garages have, if your going for a more realism.
This garage is actually going for a less modern style, leaning more towards something you’d see out of low end buildings like shopping malls or apartment buildings.
I’ll add a new image in a bit. OP will receive edits.