A fresh re-install would be the most reliable thing to do, since you've erased essential data for your applications (icons and themes is one example). The actual binaries will be in other places, like /bin and /usr/bin, so the system isn't unusable yet.
Providing you haven't written too much in the hard drive in the meantime, the data can be recovered using software.
There is a utility called testdisk, I have written a tutorial in the Tips & Tricks area of this form, originally in mind for this thread.
If recovery is a success, you can move/copy these files back to /usr/share/ where they belong. 
sudo mv /tmp/recovered_files/* /usr/share/
As mentioned previously, a fresh re-installation is always recommended.