Tiles and sprites for 2d game

I have created a small mobile game and wanted to pep it up a bit with some neat graphics. Therefore I am searching for a 2d graphics artist with pixelation skills. The items I need reworked can be seen here: [login to view URL] As you can see, there is a spaceship sprite, a turret sprite, some levels and the tilemap used for the levels. I need someone, who is able to rework these items, so they look more professional. There are in total 15 levels, that need to be made. They have all been created in a similar manner as the 3 levels displayed, so real level design wouldn't be involved. Please post a link to some of your previous work.