there are several pluggins but none specific for fantasy photos, this is achieved thru the processing in PS of several images, on several layers and using the masks to get what we want of from each of them.
Some interesting and useful plugins: onone, nik, topaz but there are many, many others. I would recomend the first two, as onone has many features inside such as old films look alike, x-processing, many kinds of b&w conversions, and others. As for the Nik, it's really good to play with the light and it allows you to process only small parts of the image without touching the rest.
Other thing you should look for is how to handle images on several layers, and how to use masks, these two things are without a doubt the best features of PS and a real treat to achieve those fantasy photos. Try googling what you specificly search, there are thousands of e-books, tutorials or videos about almost everything around PS, even howo to create those 3D images you seem to like. I leave you examples:
- Lynda.com PS CS5 creative effects
- Scott Kelby's books
- Photoshop CS5 Extended One-on-One 3D Scenes [you'll need the CS% extended version to be able to use this]
I advise you, but you should already know by now, that it will take you some (a lot) of time to get in there, but in the end the results are so worth the hours we spend experimenting...
If you want to mail me [you can do it going to my intro page on TE and use the "contact" there] i can send you an example on how to create a fantasy scene.
Hope this helps you in some way.