Yeah, you have to be a member to view files uploaded on the servers here. As far as uploading them to your site, the proper way would be to approach the artists individually by PM or e-mail if you can for permission. I think you can't send PMs until you have a certain number of posts...so maybe chat it up with some comments on finished maps you like or give one of the tutorials a go and post your works in progress.
And. Welcome to the Guild! If you want to learn to make awesome maps like the ones you've picked out you've come to the right place. I think you'll be pretty amazed at what you can do if you give it a go!