Here's some info about including image data as part of the URI: http://en.wikipedia.org/wiki/Data_URI_scheme.

Assuming the HTML is compressed, wouldn't this also achieve the same "poor-man's pipelining" result, as in less server connections? It seems to have broader browser support than the JAR thing.

Edit: I found this too... the MHTML method linked in this article is also interesting: http://danielmclaren.net/2008/03/embedding-base64-image-data...