Here’s a fun little thing I whipped up: A CGI which takes a numerical userid as a parameter and redirects to that SDMB user’s avatar URL, as found in the user’s profile (it first checks for an “SDMB Avatar: <url>” entry like here, and if not, it returns the standard SDMB profile pic URL, which ends up being a 1x1 pixel white image if the user has no profile pic or if you’re not logged in.
You can use it blindly for an <img> tag like this:
<img src="http://splitter.august20th.com/sdmbav.rb?userid=79856">
(for the nerds: it grabs and parses profile pages on-demand, caching the found urls in a database. It won’t re-snarf a profile page if it’s gotten it within the past hour.)