About the icons:
How about a small analog clock with a green check mark over top for up to date blockchain and a red "x" over the clock for not up to date.
That's a good idea, but pretty difficult to cramp icons with icons over it into a 16x16 icon, believe me, I tried

If you come up with something please post it here.
We could even have and hour glass over the clock if it's downloading representing that it's downloading. Animated hourglass would be ideal! Just like the hour glass by many mouse pointers...
That analogy is not correct as it's
always downloading, even when the whole block chain is synced. There's always new blocks and one could come in at any moment. It's a matter of being in sync or not, so the clocks idea is better.
Or do you mean the "initial download" progress bar? During that time, it could indeed show an hourglass.
I was able to succesfully build and run on Mac OS X, with the following small modification to bitcoin-qt.pro
Great, I'll update the build file for mac

Can I use that screenshot in the opening post?
Those warnings occur on any OS, and are pretty harmless. It's because I moved some stuff around, I'll fix them shortly.