The ONLY input source of data or images for Nprinting is a QV object. When you say you want to take a screen shot of a worksheet, I am guessing that this mean multiple objects. How would you capture the screen shot other than manually?
I use images all the time. Not sure what you mean by dependencies being a problem. Even if you have 5 or more images of charts in QV, it is pretty easy to drop them into an Excel template in Nprinting.
You can add an image of any sheet from the QVW, including those that are hidden.
When you add the image to your template, search for "SH" and that should return all your QVW sheets (among others). Then just drag and drop the sheet ID into your template and you'll get the same view as if you were in the QVW.