GPL v3 seems a bit much for graphical tile sets. Either you retain ownership of your art or you put it out into the public domain. What kind of restrictions does this put on game makers that want to use my tile set after the contest is over? Must they include a raw copy of my art in every free or non-free game they make?
From the rules:License: Your art must be available under the CC-BY-SA 3.0 License and the GNU GPL 3.0. You may license your art under any additional license(s) that you choose.
You can also license your work under a more permissive license in addition to GPL and CC-BY-SA if you want to, so you can make it more free, just not less free.
I'm not sure if I understand correctly; Do you have to make your own art for the first competition, and use that for the second programming competition?
What if you only want to enter the second competition, can you use art provided by the first competition from other teams?
Would be cool if you guys could also provice a list of programming languages that will be allowed, I'm having a hard time thinking of one.
Yes, that's the entire point; you use random art you steal from the first competition for use in the second competition. That's the entire point of free licenses; they allow people to steal your stuff and make new stuff with it.
As for the programming languages, I know that Java using OpenJDK is allowed. .NET using MONO, notably, is NOT allowed (or at least strongly discouraged, see the FAQ page). It would be nice if someone could compile a list of languages/libraries that could be used, yes.