Using google-fu and thanks to a helpful yahoo answers entry, I found both the actual Tengwar characters of the Sindarin in an easy to decipher format as well as a great, clear jpg of the actual gate of Moria from the LOTR book.
OR I could just put the Tengwar characters for pedo mellon a minno all fancy-like and have "Speak friend and enter" in dramatic allcaps across the bottom. I'm doing lots of crappy little thumbnails. I think what I'm going to have to do is (once I am no longer at work) go and make stencils of each element that I may want to include and just juggle them around manually to see what I like the look of best.
At this point, it's still only a model. But honestly, I kind of forgot I was planning on doing this... which is why it's taking so long. In other words, any progress is... at least progress, right?