I also recently spent about an hour serching for the same thing but to no avail. I did find a
large list of mime types, but it unfortunately
lacks a descriptive pretty name.
One resource I did discover was on my system in /usr/share/mimelnk. Within are subfolders with mime type information, including
pretty names. Below is an excerpt from the TIFF Image entry:
[Desktop Entry]
Type=MimeType
MimeType=image/tiff
Icon=image
Patterns=*.tif;*.TIF;*.TIFF;*.tiff;
Comment=TIFF Image
I was thinking of starting my own mime type database using the information from /usr/share/mimelnk as a starting point and
building from there. However, it would be much nicer if someone knew of a more comprehensive list.