Found a nice hint for all cli-lovers on OSXDaily.com

Quote from the article:

Quick Look is a nice feature added in 10.5, I use it often for glancing at the content of various documents and it certainly beats launching an application. If you’re an avid command line user though, you may be browsing through a directories contents and wondering just what is that JPG or DOC file. Wonder no more, because you can easily use Quick Look from the command line:

From the command line, use the following syntax:

qlmanage -p filename.jpg

This will launch a Quick Look window with whatever file is specified as ‘filename.jpg’, the file type can be anything that Quick Look is compatible with (which seems to be just about everything).