Well you'll definitely get the attention of LOTR fans but it may be slightly, shall we say, off-putting to those who do not like LOTR. You do not have to fully commit to a theme but people who hear about your server may think you did. But if you only "advertise" it as <whatever it's called> but don't mention the theme do anyone (outside your circle of friends, supporters, etc., that is) then you may get more people, and if people recognize Edoras then great and they'll tell their friends who presumably like LOTR too. But people who don't will just assume it another medieval-ish server. I heard about a restaurant that used this tactic and it worked great for them, servers are more than a little like mini businesses, they need people in order to thrive and the more people the better.
I hope this helps and that it wasn't too boring.