Probably to make the mountains and the astronaut taller.
But yeah, mixing bittage=no.
First off, note that ripping is not received well on this forum, it just gets that way when you've got a lot of people who know how hard it is to work on something and then just have it filched. As artists, ripped art is a big thing. Look at it this way; how would you feel if someone took a game you worked hard on and then just put their own graphics without asking? Yeah.
Next, onto the graphics.
The graphics you actually made are ok, but they don't match the "stolen" mountains.The detail on the mountains just screams for craters and bumps and whatnot. The earth is not terrible, but the blur effect does not work.
You probably feel wronged, along the lines of "I just wanted to show a game, and I get this crap, what the hell!!", but try to see it from an art forum's viewpoint.