Maybe a metal ribbon outline to fill the gap? What do you think?

Yeah...  You might be able to pull that off...  You're best bet is to practice first...

You could use a metal ribbon I suppose.  1/16" brass could be interesting.

BTW:  Monument company = tombstone store.  

I have done inlay work before,  You can buy pre-cut oak letters at local craft stores,  What i have done in the past is,  trace the letters on to the base wood,  score a line INSIDE the traced line with an exacto knife.  The use fine wood working chisels and a tiny hammer (avaiable at home depot, dont get the cheap ones they dont wok as well as the more costly ones,  the smaller the hammer the easier it is to not scew up) to remove the wood so the letter will fit in.  check often,  leave the letter protruding slightly from the base wood then sand until flush..  with a tight fit you dont even need glue to hold,  use an acrylic shellac, as it dries it will lock the 2 pieces together.

ktrim, that sounds PERFECT! Like I said earlier, I don't have much art skills so having that done will help a lot. It also allows me to concentrate on doing the dovetail right.

Okay, so I got my board today (no maple or oak, I had to settle on poplar because I'm so poor) and I went to get those pre-cut oak letters from the craft store as ktrim suggested, but they didn't have anything that looked very nice. They had the big blocky ones that looked as if they belonged on a child's toy of some sort. Very blocky, not elegant at all.

I found some stencils there that had the lettering I wanted, but I don't know what I could do with them. Someone mentioned etching plexiglass and using it as a "window" type thing? How could I do that? How could I get the plexiglass in the wood without splitting the wood?

Or...

Does anyone know where I could get some more elegant lettering? Should I just check around at different stores?

Or...

Any other ideas of how to do the lettering on the side?

Get the big blocky letters and trim them into a more attractive design.  Cut them with an exacto and then trace the newly shapped letters onto the box.  Then follow Ktrim's advice.  

If you need help with the letters, go down to the art dept at your local university and hang out until you can get some dirt hippy to help you.

I got some nicer letters from a different hobby store. The letters are M and B, and the most rightward line on the M is going to mate with the vertical line on the B. I don't know wether or not I'll offset the two or not, but we'll see. That will fit nicely on one side, but the other side is empty so far. Any ideas of what else I could put on there, or should I just put another M & B combination?