It seems you focused most on the shrooms themselves, and if that's the case the extra effort you put in to the environment and background really paid off ( for me ) to not only create the shrooms but also to create a glimpse of the world which they inhabit.
The shroom design definitely feels quite unique to you, as it's not something I've seen anywhere else, which I greatly appreciated. They feel very alien, yet still believable ( you achieved a good balance in that regard ).
Overall, I feel this piece as a whole, the shroom design, and the scene itself all work together to create a compelling concept. Nice work!