This is a quick guide on how to open up the NVIDIA SHIELD Tablet (2014). I couldn't find one, so I figured I write one.
On close inspection, there is a thin seam along side of the device towards the back.
I used a plastic opening tool from IFIXIT to wedge the seam apart.
It wasn't too hard to work the end of the tool into the seam and make a little space.
After a bit of space was made, it was fairly easy to slide the bladed side of a spudger all the way along the seam and work the plastic back off. There are several small plastic tabs that hold the back in place, so you need to be careful not to use to much force and damage them. It helps to remove the stylus from the case, and the back is firmly held on around the camera area on the back.
Once the seam has been loosend the entire way around the case, you can simply remove the plastic case backing. If you have the LTE model like I do, you need to be careful not to pull the back away from the rest of the device as there is an antenna glued to the underside of the backing. There is a small connector where the antenna can be removed, but there is plenty of slack to use it like a hinge without removing it.
Opening the shield was very easy. You only need a couple of prying tools.