Is this cotton or viscose?
Yes, the picture should be sufficient to decide between viscose and cotton; see photo of cotton at http://whrhs-forensic-chem-spring-2010.wikispaces.com/Fiber+Analysis?responseToken=906bf6a76a5e268a00e54c8bce6927ba.

Recall that cotton was the cell wall of a plant cell, so it retains some of the shape of the cell. (Silk, on the other hand, is excreted from spinnerets, as are man-made fibers, so it looks more like viscose).