Like, if you’re a beginner artist and don’t have enough time to properly sit down and push out new designs then the WLF contest might do you some good if you want to undersell your design for quick cash.
The thing is though, once you sell your design to them then that’s it. You can’t put it up on Society6, RedBubble, or any other sites that offer that sort of service. That design is no longer yours, it’s theirs.
If I were you, I would just look for other options and ways to get my work across. So far Society6 has been doing pretty good with me and while it’s not a lot of money, I at least still OWN my designs and can do with them what I want and when I want.
What Steve said!