[Please click the image to see the example as the thumb is too small to read]

I see that Garlor wants to,

include keyword data which can be read by search engines

How do you know that internet search engnes are programmed to look inside
image files (jpg, ...) to read the EXIF information? 

While you're waiting to discover that answer, why not try, ...

"Now for something completely different" ...

I think it would be easier to have your web designer include 2 additional
information fields with each image: Image Title, and Image Keywords. 

Having that available, insert that information into the heading part of the
generated html coding.  ... as shown in the attached example. 

HTH but YMMV ...

--
Martin