I was chasing down another issue (slow "Save As") and thought these two issues may have been related (with QuickLook being the common broken link). Unfortunately, my "Save As" dialog is still miserably slow on the initial load; but IconServicesAgent hasn't gone above 30MB and he rarely makes an appearance in the Console!
Some of these steps may not be necessary, but here are all of the steps I took that inadverdently put IconServicesAgent back in its place. Note: all commands are a single-line, if they appear to be multiple that's just the forum formatting.
Check for any QuickLooks related .plist files. In a terminal:
mdfind com.apple.quicklook. -name .plist
I only had files at the system level (specifically within /System/Library/LaunchAgents/). If you have others, modify the directions below to take that into account (re-introducing plist files from the system level back up to the user).
Make some temporary directories to store these plist files, just in case: