This is quite the interesting read...
http://www.jaapl.org/cgi/reprint/36/2/240.pdf
"Naked suicide can be associated with any method of suicide; however, anecdotal evidence indicates that it occurs more frequently with
hanging, overdose, or drowning, but to a lesser extent in jumping deaths. With the exception of jumping, most naked suicides occur indoors."
"Anger and vengeance can be expressed by completing suicide while naked, especially when it is intended to traumatize a survivor. The shock of discovering a naked suicide inflicts an indelible, traumatic memory that can haunt a survivor for a lifetime."
"The person who completes suicide while naked may intend to add insult to a suicide survivors already devastating injury."
"Clothes may be partially or completely removed to facilitate the method of suicide. For example, the individual may remove or reposition clothing to expose the wound site. A shirt may be removed to make hanging easier or to be used as a noose."