Hello Pixelation! I'm like everyone else and think I can make games and I've started by making a grassfloor/mudwall tileset just like everyone else

This is the first iteration and now that I'm finally done with at least that for each tile for the grass floor and mud/rock walls I'd thought I'd get some critique on it to help improve it.

Here is the tileset:


Here is a mockup made with some tiling tool:


I've run it in my level generator and it covers all possibilities that can arise in the heightmap->tilemap transformation (that I've seen ).
The grass doesn't look that great in larger patches but I intend to break it up with patches of gravel and taller grass so I'm not that worried about that. The part I'm really disappointed about and would like your input on most of all is the mud/rock/turd walls. They are an obvious level worse than the grass tiles. I would love for them to look more natural but I can't really figure it out.

Also, because the whole worlds terrain will be generated I'm not sure I can add shadows to tiles, I might try to generate some full screen shadowing based on tile types and heightmap but I doubt I will draw specific shadow versions of the tiles I have. So everything is pretty bright which currently makes it look unnecessarily flat.

All critique will be greatly appreciated, thx!