There are two alternative interpretations to answering this question, both of which are very important.
First, and critically, players doing this are signalling that they don't want to stay dead. Turning around and saying "No!" means that you're negating a player wish. Certainly allow them to specify what level of body part is needed for resurrection. Toss the question onto the players, especially if one of them is a wizard, and try to this in character. Then, inform them that the entire world will be held to the same rules. Let them decide the consequences and hardships they want, don't impose arbitrary hardships on them.
Fun, and more to the point, antagonisism, don't come from negation. Allow the players to be crafty, reward them for having excellent ideas, and then insure that they're aware of the ultimate consequences of their actions. This means that they've had an impact on the game world, instead of a fun-destroying No!. Never say no. It's boring.
Secondly, looking at the problem in the 4e world from an Ars Magica perspective, fingernails and hair can certainly be used as Arcane Connections to a body. Perhaps, taking a page from that, the 4e DM could request that such ephemera be "enchanted" to form a "lasting connection" to the person. Of course warn them that many rituals can use such a lasting connection. The law of sympathy, from actual magic theory certainly holds that a fingernail is as good as a person. Let it be so in 4e. Let there be Magic!
Then let there be complications! Not all the time, cause that too is boring. But it's details like these which inform the game world, and give the choices of the players weight. Dying is boring, or exciting. Let the players decide. All of their decisions have interesting corruptions and consequences, so there's no need to restrict the design space!
The Rules Compendium has what you're looking for.
The Rules Compendium, p 295, has random loot tables in lieu of treasure parcels. This answer discusses the fundamental mechanics, It also looks like someone has made an excel spreadsheet to do the rolling for you.
Best Answer
Yes, but it's almost always pointless.
4th Edition has a different conception of items/treasure than do previous games. Treasure, as a component of character, scales greatly with character and is worth very little outside that context. The astonishing increase in purchase costs for common enchanted items means that non-enchanted items are, in my experienced, always glossed over unless they're relevant to the plot.
Functionally speaking, any unanticipated looting that players engaged in should, technically, be subtracted from future treasure parcels. (Make sure to subtract the correct amount though (i.e. the sale price of the item.) Usually, this effort is also not worth the effort.