The tiny icon (this one http://sstatic.net/so/img/tag-postgresql.png) on the PostgreSQL tag is nasty. Could we change it to use the favicon from their website ()?
If you notice, when you go to the tag page you linked to, at the top of the page it explains why the icon is as it is.
The icons for the tags do not necessarily represent the product the tag is describing. The icons represent a company that is paying to have their logo next to that tag. In this case Command Prompt Inc. is sponsoring the
postgresql tag, which is why the tag carries the Command Prompt logo, not the Postgres logo.
Sponsored tags have been discussed extensively here on meta.