I was shown this sometime ago by a fellow Dreamlight member tugpsx_gfx. This works for Daz Studio only as far as I am aware.
Get yourself a cool picture of a pose. Here I grabbed one off Google and it is small about 300 x 200.
With Daz Studio open load a figure first and then go to Edit > Backdrop
( See image 1) I have found that loading Genesis after the backdrop the backdrop image gets removed.
This will open the Backdrop Options
window (See image 2)
At the top where it says Image: None click on the word None and Browse
to where your pose image is stored. (see image 3) Select your Image and click Open.
You should end up with something like Image 4. Looking though the camera the image stays in the same place and doesn’t move around when you move the camera. This is true for all the Orthographic cameras, front, back etc. Also the aspect ratio of your rendered image will have an impact on how much your reference image stretches. I used a Portrait aspect ratio which reduced the sideways stretch.
Line up your figure following Jaderail’s advice on page one, get the hip in place first and the rest should follow. You may have to zoom in or out to match the size of the figure in your reference image.
This is what I got after an hour of tweaking. (See Image 5) I did have to turn off limits to get the arms in the right place
Just remember to remove the Backdrop before rendering.
I suppose you could do this with a Plane in any software, applying your pose image to the plane.