Attached Link: http://www.uvmapper.com/uvmapper.htm

The good news is that I can give you the answer, the bad news is that it could be extremely confusing.. :( There is NO set size for Poser "skins". If you don't have templates for the items that you are trying to make textures for, it is however, a reasonably simple process to create them. The first thing that you are going to need is the program UVmapper (see link). After you've installed UVmapper just fire up Poser select the item that you need a template for and export a copy of it as an obj file. Start up UVmapper and load the obj file into it, if the object already has a UV map it will appear as the default map. It is then a simple matter to export this map as a bmp file and use it to create whatever texture you require. If the obj file doesn't have a uv map then you will have to use UVmapper to create a new one. Obviously you will probabbly do better to read the help files on the site in the link, as I can't really do justice to this subject in the forum. Hope that this has helped :)