I was going to pixel a big pile of hay on his back like in the reference, but i was unable to make it look nice.  So i just cropped it out so I could enter the weekly challenge. 

Where is the burden! He's missing a rider or a big pack of corn!

The sand texture you added is very uniquie... but very cool. I thought "Battery Operated Boyfriend" was a fantastic idea, by the way.

This has been a true beast of burden for me!   Made a new edit.. hope it's better. 

Poor animal, I bet he is very tired and thirsty, he looks so sad!

Ground could use some work, looks like a bunch of random dots, no texture.

Edit: Yeah I see you fixed the ground. I think it could be more like small dunes, right now it looks just like lines, but this is much better than the previous ground.

Nicely done, although I would add some dirt to the ground instead of just one color.