Hi -
It depends on the version of SQS you are using. The current API
version places an 8KB limit on message size. The previous API
version, which is deprecated but will continue to be supported for a
while, limited messages to 256KB.
AWS is strongly encouraging people to move to the new API (and
corresponding pricing) but because a couple of previously supported
features did not make it into the latest version they are still
providing support for the previous API version.
Mitch