What Linux can do:

Work with images as in Photoshop - using Gimp.
Create desk top publishing documents saved as eps or pdf files
Open MS office documents with Open Office
Play, record, edit, and save music files, and convert them to MP3 if required
Write CDs and DVDs in formats readable on any operating system
Design and create web sites
Let you access the web, collect and send e-mail (much of the web is run on Linux)
Watch TV (if you have a TV card) watch DVD films.
Edit and create film (many feature films are now created on Linux based software)

What it can't do:
not much