This question was pretty much answered in the comments, so I will just give some relevant references:

*Geometric structures on manifolds and varieties of representations,* by W. Goldman, Geometry of group representations (Boulder, CO, 1987), 169–198, Contemp. Math., 74, Amer. Math. Soc., Providence, RI, 1988.
*Locally homogeneous geometric manifolds*, by W. Goldman, Proceedings of the 2010 International Congress of Mathematicians, Hyderabad, India (2010), 717-744, Hindustan Book Agency, New Delhi, India

The above two references describe the general picture pretty well: the moduli space of marked $(G,X)$-structures on a smooth compact manifold is locally modeled on the character variety (in some sense).

In practice, regardless of the properties of the holonomy map, one often uses the structure of the character variety to determine the structure of the moduli space of $(G,X)$-structures. This is exemplified well in Section 4 of this:

*Trace coordinates on Fricke spaces of some simple hyperbolic surfaces*, by W. Goldman, Handbook of Teichmüller theory. Vol. II, 611-684, IRMA Lect. Math. Theor. Phys., 13, Eur. Math. Soc., Zürich, 2009

W. Goldman has also made available his working book on the subject: *Geometric structures on manifolds*, which contains many detailed examples.