If you fix or remove the perspective for the zombie on the ground, you have a very peculiar but interesting perspective overall. But I think the sketch needs more finish before a more constructive critique can be offered.
The zombie lying by his feet looks very weird. It's too small, and his legs look like they are in a unnatural position. Also, The stance that the gunner is in looks quite awkward, and the zombie on the bottom right doesn't look like he's just been shot. His head would snap back. Try to clean up your lines as well.
Posts
Hiking Essentials