If you are working with Poser 4 or higher, then all the textures, bump maps, trans maps etc. are located in your Poser4/Runtime/Textures folder (or any subfolder thereof). Transparancy maps are greyscale (black=invisible, white=visible and shades of grey are partially transparent). They can be any image format type that poser accepts, including .jpg (which is what most people use because of file size). They do NOT have to be 8 bit files - they can be 24 bit, But poser will only use the luminance information for transparancy.