Yes. Here's how:
iOS -> tap the green camera button > tap "Choose" on the camera screen > Allow the app permission to access your device's photo gallery (optional, but necessary for uploading photos).
Android -> tap your Profile button (smiley icon) > Settings > toggle on "Offer option to use photo from gallery".
Then go back to the home screen and press the green camera button. Select "Gallery" from the pop-up notification asking you if you would like to take a photo or select from Gallery.