Separate 3D images are ok to show how the cover will look, but our members are unable to give you advice on a 3D image so make sure you have a flat 2D image as described in the first post before you add a 3D version.
I have provided action files, for use in Photoshop, that will create flat previews perfect for Work In Progress covers. By splitting the image into 3 pieces, it allows you to clearly see what the 3 individual parts of the cover would look like, as well as the overall design. While it is not going to become a rule of the site to make you use this method of previewing WIP's, I would like to encourage all members to do so. Each download comes with full instructions, a PSD file and a ATN file. The PSD file contains the template of the case, and the action contains all the necessary commands to put the preview together. Simply load the preview PSD, paste your cover and hit play! All you have to do then is save

Download the DVD preview here
Download the BluRay 3173x1762 (127 spine) preview here or
3118x1748 (143 spine) here.