com.apple.IconServices taking up large amounts of disk space - why?
To be frank, I wouldn't worry too much about it. You have plenty of space left. My IconServices folder was about 4 GB large and I had 3 GB of space left on my 160 GB SSD.

I can't tell you why Apple is creating or caching those files on OS X, sadly it seems to be a kind of mystery. I wasn't able to find out anything.

Anyway, after booting my Mac in safe mode (holding down the shift key on startup until the progress bar appears) and then booting up again, I ended up with 13 GB of free space. Try this to free up more space.