Use Default Avatar in gravatar

With Gravatar you just add a new email to your account using sub-addressing and set up a new image attached with each of the different versions of the same email address.

E.g. Your base email address is user@example.com, with sub-addressing, this can become any of the following:

• user+lifehacker@example.com
• user+candystand@example.com
• user+keepfearalive@example.com

Set those up in Gravatar and use them to register for the various sites.

If you're using an email provider that allows sub-addressing (or plus-addressing if you're familiar with Gmail) and the site you register at allows you to use an email address with sub-addressing, this will definitely work.

Some sites will consider an email with a plus as invalid, so this won't work for them.

Five years later, but you can now (and for quite some time) add additional email addresses to your Gravatar account. Just log in to your account, add the email address, click the link in the confirm email and you are done.

Still not as easy an practical as a "+" wildcard, but quite doable.