I agree with Ghast, the flare could have been used better and the lighting is a little off. The unicorn seems a little out of place, it kind of looks like you just put a few renders together with a filter or two on top. I'd suggest some hue-saturation adjustments, adjusting the flare and lighting effects, and something with the unicorn, though I can't exactly place my finger on it... maybe move it down a bit and add a drop shadow type effect to make it look a little more natural to the overall image. I do, however, like the mystical feel you've cultivated very well and the slightly-psychedelic color scheme. I'd love to see it again after some further editing!