A neat research tool is to go to the Libary of Congress
http://memory.loc.gov/ammem/cwphtml/cwphome.html

Browse the selection and pick out the photos with tents shown. Download the archival TIFF version of these photos and save them. Open them with a decent photo program and use the zoom feature to look at what you want. You would be surprised at the detail in these images. Some you can even tell what type buttons the soldiers are wearing. Should be able to find what you want in the way of tent poles.

One photo that springs to mind is the one taken from the observation tower behind Ft. Fisher in Petersburg. The army has left and all that is standing are stick frames where the huts were. The bad side is that this photo does not have great resolution. It would be worth a look.