the corpse name is actually an attribute of the class type, so by default, you cannot change the name of the corpse for individual instances of creatures.
But a simple modification to the GetCorpseName method in Corpse.cs will let you do it

For this sort of thing I make use of the XmlData attachment that allows you to dynamically add a new data to objects. In this case you would add a new CorpseName property that can be checked in GetCorpseName.
Just make this change in Corpse.cs
Then when you spawn a creature, you can give the corpse any name you want. Like
orc/ATTACH/xmldata,CorpseName,a slimy little corpse
where CorpseName is the name of the attachment, and "a slimy little corpse" is the string data.

To get a highly personalized corpse name like that (each orc will have his own named corpse), place these two spawn entries in subgroup 1
orc
SETONSPAWN,1/ATTACH/xmldata,CorpseName,the slimy little corpse of the miserable {GETONSPAWN,1,name}
the first entry spawns the orc, and the second adds the CorpseName with the actual name of the orc in the first entry substituted at the end.