How to sell Pictures Online to get an extra income?

One way to earn extra income by selling photos online, there is much demand for Photoshop creations and also original photos, it is best to look for what people ask and do it, so I've heard of commissions, where people can suggest something you do and people pay and then send them or you can set a price for something. a good website that many people sell their art is deviantart.com you make an account and you can ask for commissions. There are also etsy.com