If new photo in your Dropbox folder , then create a post on your WordPress blog
If new photo in your folder IFTTT/Gmail Attachments, then create a post on your WordPress blog. Works in conjunction with Save all your Gmail Attachments to Dropbox by linden (https://ifttt.com/recipes/98759-save-all-your-gmail-attachments-to-dropbox) to publish images received in Gmail to your WordPress blog. Simply make sure both recipes use the same folder/subfolder e.g. IFTTT/Gmail Attachments. Change the folder/subfolder to wherever you are storing your images in Dropbox to have them published to your WordPress blog.