Hey Richard, sure thing, try the 'Editorial Assistant by Zemanta' plugin, it offers you related, copyright cleared images as you type, which you can easily insert in your freshly composed posts (or older ones, doesn't matter).
Here's the demo version of it, if you wish to play it first, before installing it: http://www.zemanta.com/demo/
And here's the link to the plugin itself: http://wordpress.org/plugins/zemanta/
But please note, that you'll have to un-tick the box next to "Display Related Content (Articles) on Compose Screen" option first, in your current plugin ('Related Posts' plugin), before installing this new one ('Editorial Assistant by Zemanta'), in order to avoid any widget display errors.
Either way, do let me know how it goes or if you have any more questions what-so-ever, since I'll gladly help!
Take care & have a nice day!