If you are on Linux or willing to boot a Linux LiveDVD, you can use simple commands for that, something in the line of:

find -iname "*.jpg" -print0 | xargs -0 exiftool -a | grep "Image Width"

• find is used for searching for files,
• iname is used for case insensitive filename matching,
• print0 basically uses \0 character terminated filenames as outputs, so if you have spaces in the filename, that does not create a problem,
• xargs is your magic tool, basically receiving those filenames (-0 means that filenames end with \0 characters), it uses exiftool for each file
• grep searches for the line with the text in quotes.

You can try these actually as well, just to see what is going on:

find -iname "*.jpg"

find -iname "*.jpg" -print0 | xargs -0 exiftool

You can get more info with

• man find
• man xargs
• man exiftool
• man grep

Now, instead of "grep", you can save data to .csv for each image, and do a few lines of post-processing. Alternatively, if you create a simple postprocess.sh script, you can use:

find -iname "*.jpg" -print0 | xargs -0 postprocess.sh

and in postprocess.sh use exiftool $1 to extract the data and potentially create an inventory of tags.