When completing your profile, you can upload a profile picture. We recommend you use a picture that's at least 150 by 150 pixels.
The same goes for uploading your company picture. We recommend using a picture that's at least 150 by 150 pixels.
You can upload a background image at Styles at Company settings if you want to personalize your account. The optimal aspect ratio of the image for the style is 16:9. Uploading a 1600 by 900 resolution background is usually a safe choice. You can also go bigger with the resolution as long as it's still 16:9 aspect ratio and as long as the file is not bigger than 2MB.