ok, first, light: it's obvious that the light in the background photo is coming from up right (as you can see on that rock and it's shadow on the right side), so you have to mach it somehow. right now, you seem to have your main light coming from front, one weeker from the right and probably another week one from the left. see how dark the those shadows on the rocks are? you'll have to adjust your lights to have the same impression. secondly, background: the photo is just not good enough. it isn't sharp and it's scanned with way too low resolution and than badly sharpened. find a new one - you'll never get that blurry look on your figures nor it's desirable... thirdly, props: if you are going for the realism, than you'll have to consider that water isn't just a blue filter, but an object with reflections and refractions, uneven surface and caustics. it's almost impossible to achive this in poser, and if you don't do it, you'll always have big problems in adjusting your photo realistic backgrounds to the plastic look of the figure and props. finally, i can suggest that you start looking on the photographs that depicts similar scenes and analyze them piece by piece. lighting, perspective and materials. you're right, it IS a science in itself ;)