Idea of Upload to Cloud Icon
The icon for upload to cloud is a cloud with an arrow pointing up. Since you are loading the images on a cloud service the arrow pointing up represents the images going into the cloud system that keeps the pictures out of your device but still easily accessible.
This Upload to Cloud icon is made in Material Design style
developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 6,200 icons, all in the same style and quality.