I'm currently trying to find a workflow that is best for me. I usually tend to draw better on paper or in my sketchbook first which is what I have been doing with these monster creatures, then scan them in. I then take the drawing and paint it digitally in Photoshop, maybe changing a few features of the design, then try and place my design into one of my photos.
Here is a rough example of the first two steps of this process:
However this process seems to prove a bit difficult as when I come to trying to place the monster into a photo I have to then edit it to make it fit in. I think I may have to end up extending the process so that I first get a photo up in photoshop, roughly draw a sketchy monster into it in a position I want it to be in. Then print that out and draw over it in pencil on paper so that the drawing is a lot nicer, then scan that back in to be painted and placed in a photo. It is a hell of a lot lengthier but I think that will ensure the work looks its best.