if your charachter is just dialed from the existing morphs , you would create a Morph pose file that sets the character . And create a mat pose file to apply all the materials to it. Thats easy to do in poser 7 by saving a material collection and editing it to be a mat pose pz2 file .  The character Morph pose is just save a pose file including morph channels with the figure in the zero pose .

Just document that your character pose must be applied before posing the figure .
If you have custom morphs you would need to make them inj morphs , which isnt hard , but is a bit tedious and there is a tutorial on how to do it , its an edit of the cr2 file and creation of a inj pose from that info.

If you expect to do many there are several inj pose builder applications at Daz3d.

The png is created automatically when you save to the library , but you can do more detailed ones by rendering the bits you want at 90 x 90 and adding text in a paint program . They need to be png files for poser 5 and up. rsr files for poser 4 .