Not many companies I know of that will take a design and pay a comission for it. In fact... I don't know of any.
The problem with that is... the only way to show them your designs is to send them a picture, which leaves the chance that your design will be stolen.
Also it puts risk on them because if your designs don't sell, then they've payed you for nothing and they have a whole bunch of stock that won't sell. (assuming by commision you mean being payed every time the design is used, but not necessarily sold.)
If you want to try getting money for t-shirt designs, why not use threadless, the winners are paid and their designs are then printed. There are other contest sites as well.
If your designs are good, you could make some mula.
There are dozen of print-on-demand t-shirt companies where you can upload your design. Once they sell your items you can a cut of money.
One thing worth your noting is that not all of them ship outside the USA. Cafepress and Zazzle do but the shipping rates are of very great difference. Of course there are some European based POD companies shipping across Europe. But their postage for flying outside the EU region is.... you better look for yourself : )
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