See if auto fit where you attached the image (background?) is turned on or not.  If the background image doesn't match the resolution output, you can also expect something to get distorted.  Since you can't postwork, change the dimensions of the image in poser.

Another useful tip for you is to not attach the image to the background, but to the one sided square prop.  Use the x and y scales to get it into proportion with your background image and the main scale to get it to fit in your render area.  Then you can just move the prop around or rescale it as you need to.

WARK!

Thus Spoketh Winterclaw: a blog about a Winterclaw who speaks from time to time.

 

(using Poser Pro 2014 SR3, on 64 bit Win 7, poser units are inches.)