I'm not sure why you need an RSR for your texture, but to create an RSR from scratch:

1.) Get RSR Converter(At the very bottum of the page)

2.) In Photoshop(Or whatever...) create a 91x91 pixels image, and save it as a .PICT.

3.) Load your .PICT into RSR Converter, and export your .RSR.

Poser has stopped using .RSRs.  The new format for .RSR is .PNG.  To create a .PNG from scratch:

1.) In Photoshop(Or Whatever...) create and image, and just save it as a 91 x 91 pixel .PNG!  You don't need to save as 91x91 pixels, but the Poser library thumbnails are 91 pixels wide.  Sometimes you see thumbnails that are 91x182 that are interesting, but if you forget to resize then the Poser library WILL display the whole image!

Another quick way to get an .RSR or .PNG is to make a copy of an existing(to a seperate directory,) rename, and paste wherever!

=  )