Did I created it?

If you started on a drawing Pad then you created it. ( I mean Pencil and Paper)
If you sat there playing with shapes and effects colors and more shapes and compounding etc... You created it.
When You opened up your browser and looked for Ideas, you are now getting into dangerous territory. No one says that you can't look at pictures of bridges till you find the perfect shape, and as long as you freehand the bridge then you created it. If you took the bridge and traced using the pen tool well you answer the question did you create it?
So after you traced it you repositioned it slightly and maybe even gave it a haircut. I will ask you did you create it? If you have to think if you created the design 100 % then you need to reconsider entering it. There are many designers here that look for the tell tale signs, I will not list them because those are the ones that will get you caught. It is one thing when you use the same font and totally another when you use the same brush strokes. So Before you enter the next logo in that contest ask yourself, did I create it? You will get caught eventually. As an Artist you need to have integrity. Integrity means that you do the right thing even when no one is looking. Beware there are people looking so don't compromise your integrity.