The gravel doesn't allow moisture to stay long enough to decay to be conducive to nest.
Ants love that tile. I would gravel it or get rid of it
Plastic barriers will retain moisture for long time being conducive for ants to nest.
The retaining wall will attract ants not alot you can do about but the debris like the garden fertilizer bagged will nest under it.
SUSPECT AREAS TO KEEP AROUND THE HOUSE
Debris under the porch front door sloping in the house
Gravel the interior perimeter of the raised bed
Gravel the tile
The fence touches the house.
The grass on the foundation and the fence is suspect.
