I'm creating this bug as a follow-on from bug #137704 to keep discussion of
an Image Property Inspector/dialog separate. Sven says it is planned, but I
didn't find an existing report. So here's a suggestion:

An Image Property Inspector that inherits the General tab of the Info
dialog, showing all the stats of the Image, including Pixel Size, Print
size (in chosen Unit), Resolution, Colordepth, filesize, file location,
etc, and the ability to alter the chosen Unit for the Image (eg Inch, Pica,
Millimeter, Centimeter...) and perhaps Resolution (which alters Print size
accordingly). It would also contain any image metadata, such as digital
camera Metadata (EXIF) which contain things like shutter speed, date taken,
etc. Some useful links on that can be found at Wikipedia:
http://en.wikipedia.org/wiki/EXIF For MacGimp at least, it may contain a
Comments field, reflecting the Mac's use of Metadata to store user comments
on each file. May contain a thumbnail underneath.
The Print Size & Display Unit section currently under Image > Scale Image
would find a better home here, which incorporates the abovementioned
ability to change Resolution, without actually Resampling the image, and
changing the image Units.

Note however that although the General tab of the current Info palette
could be moved here, the Info palette (current Extended tab) with
interactive image color and cursor/marquee dimention data is needed for
color correction with the Levels and curves among others. It may also
contain Color Samples from a proposed Color Sample tool in bug #137776. 
The Info palette needs to be compact, so may not work as a tab of the Image
Property Inspector.