One thing you can do (however, it takes trial and error to get the wrinkles right) and it envolves displacement or bump maps.  What I would do is get the body texture map of the figure you are using, then in your 2D paint program use layers, your base will be the texture map, layer above will be black (disable it after so you can see the base map), on the next layer draw fine white lines for your wrinkles, that is going to be the hard part getting the lines to look like wrinkles.

Then save everthing as a .psd, .psp etc retaining the layers, name it wrinkles.  Next, enable the 2nd layer so that you have your black background -black shows depression, white maximum raised area,  getting fancy, anything in between equals less height etc).  Save that one as a .jpg.

In the material room, make a blender node and attach it to your diffuse_color channel , connect up channel one to your original body texture node,  make a texture node and import your .jpg, then connect this node to your blender node's   blending channel, adjust the color in channel 2 and adjust the blending channel's dials (intensity) to taste.

Try connecting your blender node to the Poser Surface bump or displacement channel too and adjust their dials for height.

This procedure is fairly simple and introduces you to a couple of nodes and how they work.
There are many other ways to do this envolving strictly nodes within Poser, however, they can become very complex very quickly so I wouldn't go there YET if you are a beginner.  Those nodes take baby steps because each one interacts with other ones.

I have found that the body texture uvs are quite easy to work with after you experiment a little.

Jan