Wat Pha Sorn Kaew is one of the most interesting, unique and photogenic temples in Thailand. The modern style is reminiscent in some ways of the architect Gaudi, especially in the use of mosaics.
The temple is quite new (2004) and some of it is still underway. Just the views alone of the Khao Koh valley make the drive up worth it.
The highlight is obviously the huge five seated Buddhas. If you're lucky enough to get a blue sky as a background, the contrast between the bright white statues and the sky guarantees a great photo.
There are several shops and restaurants starting to appear around, but there's no public transport, so you must go by car or with a driver.