MTG proxy cards, are usually used for casual. Some tournament also allowed proxy cards when every players agreed.
Magic the Gathering proxy cards can have many different designs. Every player can make his/her own design, or use any design download online. Some players prefer original design, there are also lots of artwork online.
About the backside, also can be any design, but most player prefer original design.
when you have artwork, and the list of cards you want. the onlything left, is to make them. how to make? check here
if you don't have time to make, you can just order any cards you want. click "how to order"