See Order of Leitbur.

So this is created from whole-cloth. Which is a shame. But it feels worse to leave an unfinished cycle.

And the obvious justificaiton for an elvish knight having reach is that they ride on giant spider. TIL that GIS doesn't honour quotes for "required to have this search term" Or maybe it thinks all elves are spiders?

"Spider elf" is amusing, but also not what I'm looking for. Merry Christmas to you too, spiderman.

I give up. How is that image "Spider archer"? It's a CAT. With a distinct lack of either bow or arrow. HOW.

Cycle is Order of Leitbur, (((Dwarven Lute-Knight))) / Order of the Crimson Peaks, (((Vodalian Knights))) / Order of Vodalia, (((Elvish Knight))) / Order of Thelon, Order of the Ebon Hand.

Currently in that order because I am a terrible person. Discussion on Order of Leitbur.

That looks like some kind of a centaur to me. Artist credit?

But it's a big cat body instead of a horse

Sadly, it's one of many images that just get credited as "pinterest". And yeah, it's a cat-taur.

I think this is your source: http://paizo.com/image/content/PathfinderACG/PZO6006-Ceoptra.jpg

Yup, that seems so. So Eric Belisle is the illustrator.