Mmh, nice looking keychain, though the things in the back may broke in the pocket
May I suggest something ?
Looking at most of your pictures, it looks like you don't chamfer the edges that much. You should IMHO, so the edges catch the light.
Well I'm a "chamfered-edge whore" personnally, I think I do it even when it's not that usefull, and if I ever have a boss I'll quickly get kicked out for spending to much time on the edges and being out of shedule

.
Well more seriously it looks like you model a lot of things with edited primitives and boolean operations and things like that, while I avoid this as much as I can, I use NURMS (for non-uniform-whatever-whatever-surface), with a meshsmooth on top of it, even for relatively mechanical objects.
Of course the meshsmooth, as the name implies, smoothes the object, and you have to chamfer (double, or triple) the edges to control the edges' smoothing, but I think you know about that as the keychain head seems to be done this way.
Anyway, even if it's a mechanical part, I would always (except for pretty far objects) chamfer (double, or better : triple) the edges.
What I don't like about unchamfered edges is that it's a "perfect edge at mollecular scale". In reality you never have such edges, except for an Xacto blade

that's why I always chamfer, I keep a relatively sharp edge, but it catches light softly.
Even though this means a hell of a mess of polygons, I prefere tripling over doubling cuz' I can keep a better control of edges.
With double edges, the way meshsmooth works, the surface adjacent to the edge will always be affected a bit by the meshsmooth, and may result in "slightly floppy" highlights. With tripled edges, the adjacent surfaces are "protected" from the meshsmooth effect.
If you use max (7 or

, the "extrude edge" option is great, with no extrusion height but an extrusion base width, you triple the edge in just a few seconds (though you'll have to edit the vertex by hand, cuz' it'll create some ugly polygons, and you only want quads).
Sure it may be longer than modified primitives, but at least you have total control of the mesh, while with primitives, once you've "booleaned" something, you can't really come back. That's why I do almost everything with NURMS/edit poly.
The tipled edge works perfectly also with regular smooth, even with a treshold pushed to 180.
About the picture with a robot ready to smash a city to pieces, do you know the manga Blame! ?
If you like cities and "rough drawings" (I mean rough as spontaneous), you'll like this manga, and may find a lot on inspiration. I like the feel of this one (I like cities, magnificient as well as weird, messy), though I prefere when it's abit more rigorous (I mean in a more realistic way than "caricatural" way^^)
I like the Babel thing too, make me think of Howl's moving castle (not that I liked the movie that much, a bit boring compared to the
AMAIZING Totoro), the concept is cool, could fit well in a weird world.