This refers to images made to wrap onto 180 and 360 degree hemispherical 'models'.
This is just like using a lattice...
To use the 180 model,
Import the 'shell' and switch to camera mode.
Rotate the model so the inside is facing you (like looking into a bowl)
Move it back in the scene and make it big enough to fill the work area...don't worry
about the bottom. You can throw in water or ground plane later.
Apply the tiff supplied in the Picture editor...Load in left, copy and paste into
middle.
Mapping Mode is Object Front.

Use as Volume material A Channel
Dots in Diffuse and Ambient in Color section.
Dot in Diffusion = 100 in Value

No Dots here:
Ambience = 100
Specularity around 22
Base Density = 100
Edge Softness and Fuzzy Factor = 0
Quality = 100

The idea behind this is by simply rotating the 'shell' you can get a different
background view very quickly.
Scene shots coming...

These look ok for far backgrounds but there's defects due to distortion towards the
center.
(these are samples and I would presume that the one's for sale are higher quality)
That's normal for panoramic shots. Once you resize it simply turn it on the 'Y' axis until you get what you want.

Oh, and make sure you smooth the 3ds - click [E] next to the model
On the left side with the smooth sphere pull the 'thermometer' up with your mouse.
About 120 degrees looks good.

On the hemispherical model and tiff you have to get inside the half sphere and crank up ambience.
You don't have to 'flip' it as you did the 180.
(Pull the object near you until you see clouds inside)
Use Cylindrical mapping.
These look best as a Volume mat with similar settings shown above
These are mostly used to make skies/environments and look great when applied.
(kind of how it would be done in 3dmax).
Visual aid here...2 views were made by rotating the shell.