iPhone iOS Design

Hello, I need some graphics for my first iOS Game. The game is named Addictive Addition and its planned to be published in the next 1-2 months. Because its my first game i want all to be perfect, especially the graphics. At the moment i don't have any idea about designing this app. The app also will come in a iPad and iPhone version and at this point i need nearly for everything graphics like stars, buttons,backgrounds, icons. If you want to take a look at the game i uploaded a little slideshow showing some screenshots. Here (Sure i will add some more views or will change the app a bit, but on the whole this is as things are now.) May we could come to an arrangement ? How much i'd have to pay ? May you could send me an idea for the mainscreen or for another screen so i could see some ideas and references from you. Thanks in advance. David E