Hi @NewBee117
You are using the SharePoint list trigger... i.e. a new item.
I have checked and a 'Picture' column does not generate thumbnails... the returned value for {thumbnail} is an empty array.
I'd always thought thumbnails were generated for image files added to a document library... I wasn't aware this worked for list items.
Are you using a picture column on the list to point to an image stored in a SharePoint library?
If so, you'll need to use the URL to construct a call to the 'Get file properties' action which will return the thumbnail URL's for the image file.
HTH
Jay