Should I go for a general background or use tilemap for performance

Hi I have a question relating to both performance and game design. I'm wanting to make a 2D TD/unit spawner(not sure of the actual name) similar to the games:

Cartoon wars:


Kingdom Wars:


Whilst I'm making a prototype of the game I was looking for free art for the floor and I came across an asset pack in unity asset store that's using a tile set and it look pretty decent and gave me some creative ideas I could do with tileset instead of just using a general floor design as show above.

So getting to the point of my question are there any disadvantages if I decided to use a tileset to design the levels rather than a general floor graphics file (not sure of the correct technical term) such as slower performance or anything else I may not be aware of?

Thanks.