Wow... I didn't know I was such a big deal! Maybe I should print this comment on a t-shirt and go crib-walking now... krkrkr :P
If you ask me, I think cross-contest-entries are a great way to spread the word and get new people aware of your contest, too... and I wouldn't felt like anyone's stepping on my shoes either. I understand the concern about people reusing old entries, but that is easy to avoid by requiring new and original work to be submitted.
What kind of advice can I gice?!
Make sure you organize this in a way so that you can continue having fun curating it. You'll be the soul of this thing and your attitude will carry the show.
Big prizes certainly help to boost popularity... but it also comes with some downsides like "low-effort-lottery-ticket-entries". That said, the #GooglyPrize owes a lot of it's popularity to the generous support of my witness supporters
Foster engagement in between the contestants themselves to make it less of a frontal stage show and more of a community activity, I think that's probably the best way to keep it a fruitful and fun past-time for everyone involved.
You might have read the posts about the Googly Prize History and Prize-Pool-Ethics, if not, these go into a lot more details about my little contest.
Reading your links now :)