Some links:
Photo composition, very useful for Poser work too
About breaking the rules
Steven Stahlberg's essay

What I see a lot in the Poser gallery here is a figure placed in the center of a vast scene - the typical NVIAT thing. (I do it myself too I guess ) Moving the figure to either side could help, and cropping the image down too. From Photoinf.com: "The most common mistake people make when taking pictures is not filling the frame with the subject. If it's a photo of granny waving from the doorstep, let's just see granny and the door, not half the houses in the street with a small granny shaped blob in the middle."