When you use a blogging client from your computer/mobile-phone to upload photos to WordPress, WordPress resizes the 
image into smaller versions (e.g. thumbnail and medium) but the URLs of these resized images aren’t returned to 
the client so it can’t use them.
If clients are altered to support this plugin, when you include photos in an entry, the entry could automagically 
include the smaller images which link to the full size version when clicked on.
There is a patch to add the functionality in this plugin into the core of WordPress: 
https://core.trac.wordpress.org/ticket/6430 
but it missed the cut-off from WordPress 3.0 so it is unlikely to to be included for some time to come.

ImageURLReturner

When an XML-RPC Wordpress client uploads a photo, this plugin add the URLs for the resized images to the response so they can be used by the client in …

Mark-k

With WordPress version 3.5 remote publishing via XML-RPC became permanently active. This plugin simulates the functionality in versions 3.4 and before. Once active, XML-RPC functioning is disabled, and it can be enabled or disabled again in the “Settings” >> “Writing” admin page.

Control XML-RPC publishing

Control remote publishing with XML-RPC from the writing settings page.

ImageURLReturner vs Control XML-RPC publishing