Another type of composite, what I do, is taking two images and layering them one on top of another. Changing the opacity of one image. Similar to a double exposure in film.
There are plenty of "filters" out there for post work within the various editing softwares. I don't use those. Nothing wrong with them, I just don't happen to have those filter, so I make due and make it up as I go. I typically take a portrait and a landscape and composite them together. It tends to take a bit of time to figure out what works and what doesn't. It's all experimentation (for me anyway). It's time consuming, but I find it worth it.