A habitat, in SuperPoke! Pets, can refer to one of two things. It can refer to a habitat background, the background which all of the other items appear in front of, or it can refer to a decorated habitat, which consists of the background, the pet and any items or effects which appear with the pet.
In Habi Makeover, a habitat background is a type of inventory item and the file name ends in .inv.spp rather than just .spp. Since it does have a .spp file extension, it can be opened in SPP Lite, just as a decorated habitat file can be.