It seems like you've been using a brush with low opacity. Check out the image specs here. A quick look reveals over 1000 colors. Perhaps you've decided on your palette, but it won't do you any good unless you use 100% opacity with your colors.
As of now, it's not only full of superfluous colors, but it's a little unclear as to what exactly it is you've began working on. If it's something you're not really done with, it's best to hold off on submitting for inclusion in the gallery. A better place to start, when you're not finished with a piece, is a w.i.p. thread in the forum. There you can experiment and get many good suggestions and assistance with your piece until it's polished and ready for final submission. It's not likely to be accepted out of the public queue until these things are addressed.
But don't give up! There's a lot of potential here and your willingness to put something you're working on out for others to experience is an awesome quality! It means you have courage and as you hone your skills and utilize your creativity, who knows where hard work will take you! Keep it up, Doujan! You can do it!
I wouldn't have known what this was if I didn't read the title. The cavern color looks too close to the surrounding color. The eleveator platform looks like its levitating and not really on a track, but maybe that's because its an aliean one. I'm also confused about what the blue and yellow stuff is at the bottom of the cavern, ore, aliean alligator creature? Idk. There looks to be circuitry paths underneath the building on the lower cliff; it looks out of place. I know its an alien quarry, but clashes too much, I guess at least for my tastes. Maybe try looking at some source material including mining schmatics (if they exist), that is not strictly photographs. I really like the idea.
I give this one alien ore vein out of five. Keep it up, Doujan. I wouldn't mind getting feedback on my stuff.