If you thought that Valve has their own designer team who are creating new kinds of skins for you to play? Well, apparently, you can make them as well, you just have to submit them and get them accepted. And then you can use them, trade on Drakelounge or just discard them
How does it work? Well, first of course you have to design the CSGO skin you have in mind. That means it has to be a full 3D design that people in Valve could evaluate. If they like the created skin, then it is added to the weapon crate. This allows players to get the skin during one of the drops.
Of course, it is unknown, how many designs are discarded as we can only see the few which get accepted. It might be done in hopes of not to discourage the people who are thinking of making them.
After the skins get accepted and used, players also get the ability to participate in skin trading in such websites like Drakelounge. If you are the person who created the skin, these websites give you the opportunity of earning even more money than you initially got for the skin.
Any person with great design skills is capable of creating a new skin that will be used in CSGO. Of course, that does not mean that every skin you create will get accepted.