Games Workshop Haradrim (except their Mumak figures, which are way too large to use) are very nice.
Historical figures that work well (and combine well with the above) are Sassanids, Mamluks, or most of the non-nomadic Persian/Iranian plateau cultures between the Arab Conquest and the Timurids, including Islamic Persian, Timurid, Khwarizmians, and Ghaznavids. Later Muslim Indian (Delhi Sultanate) also works very well.
These are all historical figures from a Seljuq plastic range. They mix well with the GW Haradrim figures that I use for many of my infantry and others for this army.
The far left figures are horse archers; the right figures are lancers (Javelin Cavalry in Triumph).
These figures are a mix of historical plastics (Seljuqs?) and GW figures.
These are all historical plastic 28mm figures, Seljuqs I believe. Work great, and when painted in the same color palette as the GW figures, mix well with them.
GW figures.
GW figures for the Mumakil (Elephants) of the Haradrim are (perhaps) acceptable for their skirmish game. They are based upon the hugely oversized Mumak of the Peter Jackson movies, which are visually stunning and completely unreasonable gaming-wise because of their enormous size.
So I wanted something that COULD fit on an 80mm square base. A bit of experimentation found these very nice Wolly Mammoth figures, which were durable plastic and so could be cut and posed (with some greenstuff modeling) and would fit on the base.
Then it was necessary to build a howdah so a large crowd of Haradrim could fight from the top of the Mumak. And to cut and mutilate and carve a mahout (driver) for the Mumakil. A selection of GW figures worked great for the crews and the top half of the mahout. The howdah is built of craft sticks and green stuff.