For the Khând warriors, Fireforge Games have coming out soon some new plastic Mongol infantry, with cavalry to follow.
https://www.facebook.com/media/set/?set ... 426&type=3Black Numenoreans are something I'm struggling with myself - i like the GW ones, and have a warband of them already, but they seem to me to be more thralls, utterly in slavery to Sauron. I want to make, essentially, inverse versions of the current numenoreans. Picture Elendil, or Isildur, but with a few more spikes, Eye of Dauron motifs, the sea bird wings turned to dragon wings, etc. It'll be a heavy job if i ever get to them, and I'm leaning towards the Perry Men at Arms as base figures.
For you, mostly it depends on what you want them to look like. You could play around with Conquest Games Normans. My Arnor is basically them, with cloaks. Perhaps make them a bit more 'evil' looking. There's plenty of opportunity to make something up with Black Numenoreans, so it's really tough to answer without giving in to my own ideas. Not much in the way of GW-esque things out there, that i know of, either.
For the Haradrim, sadly i don't believe there are any plastics that are suitably middle eastern. You could perhaps use some of the Perry Miniatures Mahdists, but hey'd be more 'far harad' to me. I do know that Fireforge, who are doing the Mongols above, have plans for Saracens to compliment their crusader ranges, so you might want to wait and see what they produce.
As for the spectres - these should be fairly simple. Either conversions of the last Alliance plastics (someone put some great ones in the WiP section recently), or any generic 'undead' miniatures painted in a more ethereal, ghostly style than usual, to ensure there's no mistaking them for clanking skeletons or ghouls. Mantic games does a good selection of plastic undead, but i couldn't comment on whether they'd fit in well with LotR minis. I've seen some nice looking clear green plastic ghosts from Reaper miniatures, in their Bones line, and I've been sorely tempted. Like this one, for instance:
http://www.reapermini.com/Miniatures/Bo ... test/77097