I like the definition on the body of the human. The face is more difficult to read though, for me. I think because the hair colour is so close to the skin colour, so the beard is confusing. I guess... either give him darker hair, or darker skin? I mean, this is a guy who's out in the sun a lot, right? He probably should have dark, leathery skin.

The club is nice. Good use of shape and shade.
It took a while to work out how to read the diplodocus. I'm trying to think how it could be made clearer, give me a while. In the meantime there's not much that gives a sense of depth. Try making things darker as they are further away from the viewer.
The grass tile is a standard "random pixel" grass tile. I'm not a big fan of those, but they're common enough. The tiling is a bit obvious, it could do with some tweaking around the edges. Look for obvious lines in the tiled image and try to break them up.
I would be more interested in grass that's less random and contains some information. Like individual flowers, weeds, etc. With a small number of 'detail' tiles you can even get away with most of your grass being a single shade. And that, in turn, can make for a clean background that makes things easier to see. Some examples here:
https://www.pinterest.co.uk/pin/394065036122555570/Again, if I get a moment I'll see if I can come up with some ideas.
Another alternative is the Stardew Valley style, where you see every individual blade, rendered with shadows and shading.
https://www.youtube.com/watch?v=2ahU0eXtFeg&t=6