I'm not nearly as good as you on piano, so I can't give you the feedback on that aspect. It sounds totally awesome to me, so I'll let someone else with more experience try to tell you what's up.
What I can point out is that the thunder and rain sample was a little overbearing on the mix. Did you EQ down some areas? Nice classical playing though, man!
The thunder is just my trick to add a little feel to it but you're right
I'm not very good at EQ, in fact I'm still practicing. Thank you very much for your feedback.
I also make Electro music ( and of course there will be more thunder, I can't help it ). Check this out