I had to do a series for art class, so I chose to personify the four horsemen using Mucha as inspiration.
I chose to combine Famine and Pestilence because of their similarity, and because the poses worked well together, and because I wanted the set to have three pictures, because I like odd numbers.
I almost didn't do Pestilence; the first horsemen being Pestilence is apocryphal, and there's debate as to whether it's a good or evil being. Most ascribe to it characteristics more in keeping with a false prophet, or instigator of civil war and in-fighting, hence the black tongue I gave him (he's the white horse, famine is the black one)
So in a way, the two of these belong together, whether you interpret the first horse as Pestilence, or Strife.