Oyster.com has launched Oyster Shots, with the ability to browse hotels by their pictures and not based on where they are geographically (ie their city). Instead, the user is invited to scroll through hotels grouped in photo categories such as: beaches, balconies, kid friendly hotels, luxury bathrooms, cabanas, etc. Even better, you can see the hotel's average rate (not sure how they are calculating this) and click to book right from the page.
This is getting advertised as an in-picture booking engine, which is not. You cannot input your dates and see rates right from the picture, but its very close to being one; however, it is a very well positioned call to action. More importantly, it highlights the importance placed by customers and retailers on getting the call to action in as many places and as easily accessible as possible.
If you are a hotelier and your website does not have a booking engine, which is prominent, on every single page, its time to update your site. If you do, how about having it right on your pictures? on your maps? on your amenities? your videos?