Most likely, you do not have the Android version of the app installed on your Chromebook. Unlike a phone or tablet, the Android versions of Google Photos and Google Drive generally do not come pre-installed on Chromebooks. Instead, the Chrome apps for Photos and Drive are pre-installed on Chromebooks.
To get Photos, Drive, or any other app to show up as an option when adding an image to a page in Squid, you must install the Android app through the Google Play Store app on your Chromebook. You can search the Play Store or use the links below for common apps:
For a video tutorial about adding images, see Squid - Add & Crop Images.