Illustration Concerns

I am worried that something is lacking from my illustrations and have developed them all further to have a block colour shadow on them. This is because i felt that the lines were too weak. Also I have changed my style slightly on this brief and produced all the illustrations in grey tints. This doesn't help with the level of boldness that I am wanting. So this is where I'm at at the moment and how I want them all to look. Hopefully this will strengthen my designs.

Autumn:

Winter: