The recommended image sizes for Business One Page are

Slider image size

Width: 1400px

height: 600px

Ratio:7:3 

Home page about section image 

Width: 100px

Height: 100px

Ratio: 1:1

Homepage service Section Image 

Width: 32px

Height: 32px

ratio: 1:1

Homepage Team Section Image Size

Width:340px

Height: 310px

Ratio: 34:31 

Homepage Testimonial Section Image Size

Width: 111px

Height: 111px

Ratio: 1:1

Portfolio Section 

Post-One: 360 px*340 px

Post-Two: 750 px*465 px

Post-Three: 360 px*505 px

Post-Four: 360 px*380 px

Post-Five: 360 px*380 px

Post featured Image (with sidebar)

Width: 750px

Height: 360px

Ratio: 75:36

Full-width Blog featured image

Width: 1170px

Height: 360px

Ratio: 117:36 

Logo / Header Image

Width: 130px

Height: 30px

Ratio: 13:3

We recommend you to use Regenerate thumbnails plugin to crop all the images if you have already uploaded the Images.