Unless you pick up alternate models from non GW
locations there really is little for options in LotR. The LotR line is a 25mm range, instead of the 28mm heroic that fantasy and 40k
are. I guess you may be able to use Chinese or Japanese ancients, but the armor wont be exact. If you are good with greenstuff though you could make them work.
Most of my conversions have been brass rod for pikes and the standard stuff like head and hand swaps to change looks a little bit.