Can I access Photos from a lost iPhone?

You can access photos from lost iPhone in two situations:

1) when iCloud Photos has been enabled on the devices - in that case, you can access photos through iCloud.com or on other Apple device by accessing your account. View your photos and videos on iCloud.com - Apple Support

2) if you didn't use iCloud Photos, the photos would be included in your iPhone backup made to iCloud or on the computer. In that case, you would need another iPhone to which you can restore the backup to access your photos:

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support