Utilising Corpses and the Problem of Consent

In response to Kurt's post 'Immortalized: Animals As Art' (4/21/2013):

The concept of rights-after-death is a fascinating one, especially where it pertains to the physical remains of the deceased.  Certainly, the law recognises such rights, in the forms of wills, inheritance laws, funeral plans, and legal restrictions on what one can do with dead human bodies.  However, the wishes of the dead appear to be, legally speaking, of less import than the wishes of the living.  For example, the legal penalty for rape in the USA is typically about eight or nine years in prison, whereas the penalty for necrophilia is often only three or so years.  Some states actually have no laws against necrophilia at all.  Clearly, the law recognises a large difference in the amount of importance of getting consent in these two instances.

Nevertheless, wishes still do evidently matter quite a lot after death - most of the objections I have heard against necrophilia (yes, I have discussed it with people - one never knows what will come up in conversation when one is a political enthusiast and philosopher!) centre around the idea that the former owner of the corpse involved did not consent to the act.  So it is not the odd or disrespectful use of the body which matters here.  Further evidence is in the legal use of donor bodies for display after plastination, which might be considered extremely odd or disrespectful - bodies sliced into pieces, presented in strange poses, with their inner workings exposed.  The important part is in the deceased party's consent.  Indeed, I believe it is quite legal to preserve a human body through taxidermy after death, provided that body's owner previously consented to the use.

Non-human animals currently have no legal rights over their remains.  How much should they have?  They cannot legally consent to anything, so should the default action be assuming that they would give no consent?  It is easy to say so in the case of something like eccentric taxidermy 'art,' but what about in the case of scientific study?  The animal sustains no harm from its body's use, so there would seem to be no objection, but in that case why not use the body for 'art?'  For that matter, why not use human bodies for 'art' also?  I am not yet sure what are the relevant differences between these situations, if indeed there are any.  Thoughts?