I think this piece has a lot of potential, there could be more of a story going on in the image however. Perhaps the mushroom people could be living inside and around the mushroom? The framing is great along with colour changes with the atmosphere too. You could add some moss to the base of the mushroom and add something which is a threat to them like a person although that may be a bit generic. Keep refining it and push the contrast a bit further
I really like where you are going with this, agreed with above it does have potential and have you laid in some very nice color. Should also check perspective of shroom cap, because from a low angle it should be rounder especially its back area. maybe you want a thick trunk for the shroomy, but I also feel it's a tad too thick. Maybe thin her out a bit, as the trunk gets closer to the cap. http://1.bp.blogspot.com/-mF2nmueOOK...mushroom+1.jpg
You can also take this advice if you want or not, but personally I think the composition is a bit too dead on in the center, you have lovely creatures and nice ambience with the mushrooms on the bg, but I feel like the first thing i intake is the big shroom above all else( rule of thirds) http://en.wikipedia.org/wiki/Rule_of_thirds. Have you considered making the trees extend a little more upwards? adding higher branches? making your canvas extend higher might help with this dead center dilema. Giving some breathing room for your audience might also take this piece from generic to original.