Confused about YOLO background images

So I have trained YOLOv5m for object detection and I am getting 97% classification accuracy and only 60% IOU. I want to use blank background images to decrease false positives but I'm confused about how the model will know which images are background images.

Currently I have a dataset.yaml file with this:

train: ./dataset/images/train
val: ./dataset/images/val

nc: 10

names: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

so there are images in the train and val folders and …

accuracy classification computervision dataset detection false false positives images iou train yaml yolo