Poser 5 has a default node-set for the Background, which includes BGPicture. Earlier versions seem to do it differently, thoiugh one of the menues. An alternative is to use the single-sided square primitive, and use the picture as a texture on that. For something like a [picture of a building. you could shift this square so that the Ground object lined up with the transition between wall and ground in the picture. If you want to get really fancy with such a square, you could use transmaps to pick out a window, or a gap between trees: this is an old method used for films calle a matte shot, where the scenery was painted on a glass plate, and the set shot through the clear area. There's a lot you can do with background pictures.