When you choose to upload a image in Crowdsource image capture, the image gets copied from your device to Google’s servers. By default, you must have a Wi-Fi connection to upload images. You can change this option in Settings: see Use cellular data for more information.
If you have cellular upload turned off in Crowdsource Settings, and you upload an image when you’re not connected to Wi-Fi, Crowdsource delays uploading until you get connected. The amount of time it takes to upload once you’re connected depends on the quality of your connection and the number and size of your images.