When it comes to graphic designing there are only two business models out there.
1. Stock Art
2. Freelance sites
In case of Upwork, fiverr and freelancer, you have already seen the issue of bidding. And it can be some of the time harder to crack into the market. So the stock art is another option. Note that techualtor pays for approved content here. But stock art sites don't pay anything unless someone buys the stock art. So though stock art site is partially like techulator. Getting paid is different concept for such sites.
This site is for selling your graphics such as vector art, flyer, logo and other concepts. This site allows 33% of the sales amount. Also the amount of sales from this site are relatively higher than any other stock website. Lot of variety on this site where you can sell the graphics.
This site is for the graphic designers who like to manipulate images. For example taking image and then editing it and selling it for stock. The earning is 33% of the sale price.
Apart from graphics design, the 3D design models are in demand. This marketplace lists such models up for selling. It pays very good amount from say 20$ per model or more. And 33% of the sale price on Envato market. Plus license fee if used in movies or youtube.
There are few other sites for graphic designers such as themeforest and codecanyon but they are more leaning towards coding than graphics. So though none of the sites online has "post it, get approved and get paid" model of techualtor for graphic designers. You get the idea that graphic designing field is competitive so stock sites are the way to sell the skills.