Jess,
I agree with you about Picasa vs Google Photos. I hope it gets implemented soon.
For images in Google Drive, it's not as straightforward to get them to show up. You have to word the url a little differently. It will be like this:
https://googledrive.com/host/<folderID>/<filename>
Where folder name will be a long unique identifier of letters and numbers and file name will be the image file name (with the extension on the end like .jpg).