Funnily, libs liek ffmpeg, mplayer (lib?) etc. also implement their
own image loader, so why don't we? Although it sounds interesting to
test out subclassing here, I don't think we'll gain anything by it
(unfortunately).

We already have jpegenc(broken)/dec and pngenc, how about implementing
some more (pngdec, gif, maybe others)? We can copy the actual
loading/saving code (this is only a few lines) from gdkpixbuf, of
course, but it'd make us not depend on gdkpixbuf for this feature,
which is a good thing if KDE would want to use such a feature later on.

Good point.  We would only be using a fraction of gdk_pixbuf's capability.

However, I have little interest in writing yet another generic image
loader when gdk_pixbuf is readily usable.  So if I write it, it will
use gdk_pixbuf directly.  If anyone cares, I can write it in such a
way that the gdk_pixbuf code can be copied into GStreamer and used if
gdk_pixbuf is not found on the system.

In HEAD CVS.  If someone wants it in 0.6, file a new backport bug.