I take all suggestions on board...
I guess I'll decide on the prize depending on how long it goes on maybe...like if it's guessed pretty quickly then it could be down to dumb luck...(and there's a whole lotta dumb on MTW), and like you say if it's after 2 or more then they've had to work at it....but that being said the prizes I'm sending so far are only MTW Fridge Magnets which are only costing me $3.49 and hopefully the extra picture views in looking for the right picture should offset that.
We'll see how it goes though...the rules can be fluid and we can change them until we find a right mix that works.