[LightBlue]

Matte painting is really hard imo. Looks more like a photomanip atm.
Also I think matte painting is done on greater scale, like full cities. So a lot of elements that make flaws unnoticable. Eitherway you've got a nice concept which you've executed decently, but you can clearly see you're new to this (which is not a bad thing, practice makes perfect!). I've only done a matte painting once and didn't really like it so I just went into full digi painting, which I enjoy a lot more. So I can't give you any usefull CnC on this subject (never done photo manips either), but keep practicing like you'd need to in any form of art and you'll improve :)
I don't feel like the sky appeals to me, it's too light/weird color. Do like the beam though, gives it a surreal twist.

Also if you ever want to get better at digi painting I'm willing to give you some tips and help you out a bit. Just shoot me a PM.

[Baghead]

I agree, I wouldn't be able to tell this was a matte painting if you hadn't said so in the OP
That being said the water is weird and it's hard to tell the reflection is even a reflection at first sight
Also the bendy water is super confusing

[Grumpys]

:o have rarely seen something like this.