this is a very stick issue!
having to dealt with this myself with what i do, the main complications arise with who owns the intellectual property of the piece, and the exact nature of the copyright that it has.
because copyright isnt an international law, u dont contend with 1 set of laws but them all!
for the case of "(say, larry elmore - the art he did for tsr/wizards of the coast)" this is because he was contracted, and most artist are placed under the same contract, that all intellectual property produced during the enforcement of the contract is property of the company that the contract is with. so not all artist have a say in what is done with their art work anyway!
in the UK we are affected by the 1957 act that carry's the bulk of the copyright law and most subsequent acts of copyright law deal with television and broadcasting.
most copyrights last for a term of 14 years, with the artist being able to then re-new their copyright after this time, the same applies for companies. for intellectual copyrights of the owner/producer of the work can last up to 70 after death or 50 years for digital work!
so unless you know exactly where the work has come from what kind of copyrights it has and who(if anybody) owns them, and that you have permission then it's really not worth going to court for!
on the other hand i agree with Big Bene, i would happily help you out and produce pieces for you, it would allow me to bulk out my portfolio a bit more and you will get permission to use the works produced.
as for the whole b&w art work that was used in the original books, that was to keep printing costs down. the stylized sepia like art on the cards was a design rather than art idea, simply because if you have too much colour in a small space then you wont be able to see what it is clearly at a glance! this is used even today with pokemon/collectible card games, where a limited palate of maybe 7 colours are used for the entire picture so as not to make it too busy to look at. count the colours on the monster cards they use the same technique. this is why anime is used a lot for this kind of thing because by its nature it only uses a limited palate with 1 level of shadow and highlights.
if you want to know more about UK copyright law then i have a more in-depth peice on it that states the exact nature of the laws, but its massive, and this reply has gone on long enough!
