Consider yourself part of the contest.
When we get closer to the deadline, I will announce what to do with the designs.
As far as winning goes, this is the type of contest where everybody who enters wins (you're going to get feedback from your peers) and the community comes in a close second, as they'll have new games to play and tutorials explaining the tricks of each.
In the art area, it's perfectly fine to use the work of others...I'm not sure what sites you're familiar with but the links page on the official DC web site has a list of all of the fan sites that have art, as well as the other forums which both have art to use as well.
http://uaf.sourceforge.net/links.html
There is a pretty good chance that one of us may be able to answer questions you might have about the graphics software you have as well.
As to the last question, traps can be whatever you think traps can be.

Seriously though, you're definition of traps pretty much covers what I think of as traps in respect to this game, but I don't think we'll exclude other definitions that people have as long as they're willing to explain them.
I'm glad you're enjoying using DC and very happy that you are using GPDL.

There are very few of us that know how to use it, since we're all self-taught. I suspect that soon you'll be able to help answer questions on the topic when they arise. But, if you have any questions about using GPDL, feel free to ask about them as well. I can't promise we'll know the answer right off, but we can usually get something worked out (especially if Paul helps us out).