Can I say a couple things? First, you are right there are a lot of maps that get ported/copied from other things. Second I believe you that it took a lot of time.
A couple suggestions to do what you want with. If you make a map that uses someone else design at the very least if you mention the original author in some form of credits that would be the nicest thing to do. I don't think you are trying to say this is you design or anything, it just looks more professional to give credit where it's due.
Secondly if you are going to copy an existing design consider adding some special things to it that make it unique. The picture looks a little bland for a final release. What about adding a skybox with some blue sky? Maybe even a nighttime version of it with moonlight shining on the map. What about a nightmare version with a fiery red twisted sky and some dead black trees around the map. Therre are a lot of ports that look very bland. Why not break that cycle and improve upon an existing map with your ideas?
I understand it's a long proccess to make maps. Don't be discouraged by Flux, his heart is in the right place making sure people credit mappers for their hard work.
