It's a shame you can't find higher resolution images of those towers because I think that looks seriously awesome. The dragons are really cool too.
I agree with Mike about the use of "arcade." The "Lord of the Arcades" title is very weird to me. The poster for Lord of the Rings doesn't say "Lord of the Posters." The movie isn't called "Lord of the Movies." The dust jacket doesn't say "Lord of the Dustjackets." Why would the arcade machine say "Lord of the Arcades"? To me it's a half measure between doing a dedicated theme and doing a generic arcade theme, and it doesn't really work as well as either.
And personally I think pairing that amazing dynamic machine with a theme so far removed from the arcade scene (as far as I know there are zero LOTR games) is a misstep. As I understand it the appeal of a dynamic marquee is being able to more accurately replicate the aesthetic of a given arcade game, but such lavish cabinet art will only lead to weird clashes. A Ms Pac Man logo in all its pink, yellow and blue glory glowing out of a Lord of the Rings cabinet will look really strange and IMO cheap, like an old cabinet that has had a new game jammed inside. An unbranded aesthetic would be more versatile
That's just my take though. If you're dedicated to a LOTR cabinet then that's your call, obviously.
Back to the side art, have you considered using the assets for the pinball machine? It would be a little pricey, but you could buy the art online and get high res work. These
are a similar idea to what you've got, and even if they're not super huge you might be able to scan them at a high enough resolution to compensate.