This is sort of the way I view it:
With most creative works, such as books, game sprites, and music, the main
things stopping them from being free are copyright and DRM. Software is
different, though: copyright and DRM are still used to prevent it from being
free, but the usual way of making software nonfree is to withhold the source
code. Without the source code, changes are impossible even if they become
legal someday.
DRM (Digital Restrictions Management) is something which deliberately attacks
freedom, so I think we should refuse anything distributed with DRM for that
reason. But with creative works which are only nonfree because of copyright,
and which don't do a functional job, it's not imperative that they be free.
Here's why: you mention that, in games for example, non-functional data such
as images are important, and that's true, but it doesn't have to be those
images; an image is an image, and one can be substituted for another
completely different image. See Freedoom, for example. In addition, if
copyright is all that's stopping the work from being free, abolishing
copyright or otherwise getting the work into the public domain (e.g. by
drastically shortening copyright) will have the desired effect. This is not
necessarily the case when technical means are what stop the work from being
free; if you don't have the source code to a program, you still can't
effectively change it even if the law isn't stopping you.
And then there's the fact that nonfree software can have malicious features,
while non-functional data such as images cannot.
So at the core, I agree; all creative works should be free, but unlike with
software, non-functional works being nonfree today is not a disaster.
