You mean like this? from RFC1341:
7.4.2 The Application/PostScript subtype
A Content-Type of "application/postscript" indicates a
PostScript program. The language is defined in
[POSTSCRIPT].
7.5 The Image Content-Type
A Content-Type of "image" indicates that the bodycontains an
image. The subtype names the specific image format. These
names are case insensitive. Two initial subtypes are "jpeg"
for the JPEG format, JFIF encoding, and "gif" for GIF format
[GIF].
...
[POSTSCRIPT] Adobe Systems, Inc., PostScript Language
Reference Manual, Addison-Wesley, 1985.
[GIF] Graphics Interchange Format (Version 89a), Compuserve,
Inc., Columbus, Ohio, 1990.
It's tough to keep folks from sticking postscript level-2 stuff in
under the name of application/postscript, but you can't blame
the MIME standard for being ambiguous in any way.
Dan