Here's a great entry level tutorial that will teach you how to model and texture a low-poly mushroom.
Widhi Muttaqien writes:
My latest multi-part tutorial covers the basic of UV Unwrapping and texture painting in Blender
I hope you guys enjoy it.
Part 1: Modeling the mushroom model
Part 2: UV unwrapping concept and process explained
Part 3: Texture painting basic
Part 4: More on texture painting and how to save the texture image properly