RDF in PNG by Ross Burton on adding RDF into PNG images with the tEXt field, like I was doing with pngmeta years ago now with a new tool PyPNG.
*Once I've fiddled with the library design a little I'll write a PNG Explorer (hmm, png:/// in Nautilus is tempting) and a Metadata Editor for PNG files. Then I'll try and do exactly the same for JPEG files. Finally of course I'll have to write the web front-end. *
I previously gave Ross pointers to the various RDF and image work (with EXIF, JPEG) for him to read up on the RDF Interest Group IRC chat such as w3photo image annotation work report recently made by Libby.