Promised to get back to you with answer concerning IM and MATPose files.  The program is primarily designed to create just figure morphs but textures can be included in those created injection files.  The easy workaround is to create your texture changes in the Material Room, save as an .mt5 material file, make a copy and move it to the Pose folder, then open the file with a text editor program.  I use TextPad as opposed to WordPad.  Change the line 'Mtl Collection' to 'Figure', save and then change the format of the file from txt to pz2.  Next time you open Poser and navigate to the Pose folder in your library, you will see a shrugging man with your file's name under it.  You will need to provide your own png thumbnail.